diff --git a/.claude-plugin/marketplace.json b/.claude-plugin/marketplace.json
index e80eb59..4969ae3 100644
--- a/.claude-plugin/marketplace.json
+++ b/.claude-plugin/marketplace.json
@@ -7,7 +7,7 @@
   },
   "metadata": {
     "description": "Claude scientific skills from K-Dense Inc",
-    "version": "1.17.0"
+    "version": "1.18.0"
   },
   "plugins": [
     {
@@ -68,6 +68,7 @@
         "./scientific-databases/ensembl-database",
         "./scientific-databases/gene-database",
         "./scientific-databases/geo-database",
+        "./scientific-databases/gwas-database",
         "./scientific-databases/hmdb-database",
         "./scientific-databases/kegg-database",
         "./scientific-databases/metabolomics-workbench-database",
diff --git a/README.md b/README.md
index 7c329f8..197bb7b 100644
--- a/README.md
+++ b/README.md
@@ -14,6 +14,7 @@ A comprehensive collection of ready-to-use scientific skills for Claude, curated
 - **ENA (European Nucleotide Archive)** - Comprehensive public repository for nucleotide sequence data and metadata with REST APIs for accessing sequences, assemblies, samples, studies, and reads; supports advanced search, taxonomy lookups, and bulk downloads via FTP/Aspera (rate limit: 50 req/sec)
 - **Ensembl** - Genome browser and bioinformatics database providing genomic annotations, sequences, variants, and comparative genomics data for 250+ vertebrate species (Release 115, 2025) with comprehensive REST API for gene lookups, sequence retrieval, variant effect prediction (VEP), ortholog finding, assembly mapping (GRCh37/GRCh38), and region analysis
 - **GEO (Gene Expression Omnibus)** - High-throughput gene expression and functional genomics data repository (264K+ studies, 8M+ samples) with microarray, RNA-seq, and expression profile access
+- **GWAS Catalog** - NHGRI-EBI catalog of published genome-wide association studies with curated SNP-trait associations (thousands of studies, genome-wide significant associations p≤5×10⁻⁸), full summary statistics, REST API access for variant/trait/gene queries, and FTP downloads for genetic epidemiology and precision medicine research
 - **HMDB (Human Metabolome Database)** - Comprehensive metabolomics resource with 220K+ metabolite entries, detailed chemical/biological data, concentration ranges, disease associations, pathways, and spectral data for metabolite identification and biomarker discovery
 - **KEGG** - Kyoto Encyclopedia of Genes and Genomes for biological pathway analysis, gene-to-pathway mapping, compound searches, and molecular interaction networks (pathway enrichment, metabolic pathways, gene annotations, drug-drug interactions, ID conversion)
 - **Metabolomics Workbench** - NIH Common Fund metabolomics data repository with 4,200+ processed studies, standardized nomenclature (RefMet), mass spectrometry searches, and comprehensive REST API for accessing metabolite structures, study metadata, experimental results, and gene/protein-metabolite associations
@@ -123,7 +124,6 @@ After installing the plugin, you can use the skill by just mentioning it. Additi
 - **DAVID** - Database for Annotation, Visualization and Integrated Discovery for functional enrichment analysis
 - **dbSNP** - NCBI's database of single nucleotide polymorphisms and short genetic variations
 - **GenBank** - NIH genetic sequence database (part of NCBI but with specific access patterns)
-- **GWAS Catalog** - NHGRI-EBI catalog of published genome-wide association studies
 - **InterPro** - Protein sequence analysis and classification with functional annotations
 - **MetaboLights** - EMBL-EBI metabolomics database with experimental data and metadata
 - **OMIM** - Online Mendelian Inheritance in Man for genetic disorders and genes
diff --git a/scientific-databases/gwas-database/SKILL.md b/scientific-databases/gwas-database/SKILL.md
new file mode 100644
index 0000000..ad21a9f
--- /dev/null
+++ b/scientific-databases/gwas-database/SKILL.md
@@ -0,0 +1,602 @@
+---
+name: gwas-database
+description: Toolkit for querying the GWAS Catalog, the NHGRI-EBI database of published genome-wide association studies. Use this skill when searching for genetic variants associated with diseases or traits, retrieving SNP-trait associations, accessing GWAS summary statistics, exploring gene-disease relationships, conducting genetic epidemiology research, or performing systematic reviews of genetic associations. Essential for human genetics, precision medicine, and genomic research.
+---
+
+# GWAS Catalog Database
+
+## Overview
+
+Facilitate access to and querying of the GWAS Catalog, a comprehensive repository of published genome-wide association studies maintained by the National Human Genome Research Institute (NHGRI) and the European Bioinformatics Institute (EBI). The catalog contains curated SNP-trait associations from thousands of GWAS publications, including genetic variants, associated traits and diseases, p-values, effect sizes, and full summary statistics for many studies.
+
+## When to Use This Skill
+
+Use this skill when queries involve:
+
+- **Genetic variant associations**: Finding SNPs associated with diseases or traits
+- **SNP lookups**: Retrieving information about specific genetic variants (rs IDs)
+- **Trait/disease searches**: Discovering genetic associations for phenotypes
+- **Gene associations**: Finding variants in or near specific genes
+- **GWAS summary statistics**: Accessing complete genome-wide association data
+- **Study metadata**: Retrieving publication and cohort information
+- **Population genetics**: Exploring ancestry-specific associations
+- **Polygenic risk scores**: Identifying variants for risk prediction models
+- **Functional genomics**: Understanding variant effects and genomic context
+- **Systematic reviews**: Comprehensive literature synthesis of genetic associations
+
+## Core Capabilities
+
+### 1. Understanding GWAS Catalog Data Structure
+
+The GWAS Catalog is organized around four core entities:
+
+- **Studies**: GWAS publications with metadata (PMID, author, cohort details)
+- **Associations**: SNP-trait associations with statistical evidence (p ≤ 5×10⁻⁸)
+- **Variants**: Genetic markers (SNPs) with genomic coordinates and alleles
+- **Traits**: Phenotypes and diseases (mapped to EFO ontology terms)
+
+**Key Identifiers:**
+- Study accessions: `GCST` IDs (e.g., GCST001234)
+- Variant IDs: `rs` numbers (e.g., rs7903146) or `variant_id` format
+- Trait IDs: EFO terms (e.g., EFO_0001360 for type 2 diabetes)
+- Gene symbols: HGNC approved names (e.g., TCF7L2)
+
+### 2. Web Interface Searches
+
+The web interface at https://www.ebi.ac.uk/gwas/ supports multiple search modes:
+
+**By Variant (rs ID):**
+```
+rs7903146
+```
+Returns all trait associations for this SNP.
+
+**By Disease/Trait:**
+```
+type 2 diabetes
+Parkinson disease
+body mass index
+```
+Returns all associated genetic variants.
+
+**By Gene:**
+```
+APOE
+TCF7L2
+```
+Returns variants in or near the gene region.
+
+**By Chromosomal Region:**
+```
+10:114000000-115000000
+```
+Returns variants in the specified genomic interval.
+
+**By Publication:**
+```
+PMID:20581827
+Author: McCarthy MI
+GCST001234
+```
+Returns study details and all reported associations.
+
+### 3. REST API Access
+
+The GWAS Catalog provides two REST APIs for programmatic access:
+
+**Base URLs:**
+- GWAS Catalog API: `https://www.ebi.ac.uk/gwas/rest/api`
+- Summary Statistics API: `https://www.ebi.ac.uk/gwas/summary-statistics/api`
+
+**API Documentation:**
+- Main API docs: https://www.ebi.ac.uk/gwas/rest/docs/api
+- Summary stats docs: https://www.ebi.ac.uk/gwas/summary-statistics/docs/
+
+**Core Endpoints:**
+
+1. **Studies endpoint** - `/studies/{accessionID}`
+   ```python
+   import requests
+
+   # Get a specific study
+   url = "https://www.ebi.ac.uk/gwas/rest/api/studies/GCST001795"
+   response = requests.get(url, headers={"Content-Type": "application/json"})
+   study = response.json()
+   ```
+
+2. **Associations endpoint** - `/associations`
+   ```python
+   # Find associations for a variant
+   variant = "rs7903146"
+   url = f"https://www.ebi.ac.uk/gwas/rest/api/singleNucleotidePolymorphisms/{variant}/associations"
+   params = {"projection": "associationBySnp"}
+   response = requests.get(url, params=params, headers={"Content-Type": "application/json"})
+   associations = response.json()
+   ```
+
+3. **Variants endpoint** - `/singleNucleotidePolymorphisms/{rsID}`
+   ```python
+   # Get variant details
+   url = "https://www.ebi.ac.uk/gwas/rest/api/singleNucleotidePolymorphisms/rs7903146"
+   response = requests.get(url, headers={"Content-Type": "application/json"})
+   variant_info = response.json()
+   ```
+
+4. **Traits endpoint** - `/efoTraits/{efoID}`
+   ```python
+   # Get trait information
+   url = "https://www.ebi.ac.uk/gwas/rest/api/efoTraits/EFO_0001360"
+   response = requests.get(url, headers={"Content-Type": "application/json"})
+   trait_info = response.json()
+   ```
+
+### 4. Query Examples and Patterns
+
+**Example 1: Find all associations for a disease**
+```python
+import requests
+
+trait = "EFO_0001360"  # Type 2 diabetes
+base_url = "https://www.ebi.ac.uk/gwas/rest/api"
+
+# Query associations for this trait
+url = f"{base_url}/efoTraits/{trait}/associations"
+response = requests.get(url, headers={"Content-Type": "application/json"})
+associations = response.json()
+
+# Process results
+for assoc in associations.get('_embedded', {}).get('associations', []):
+    variant = assoc.get('rsId')
+    pvalue = assoc.get('pvalue')
+    risk_allele = assoc.get('strongestAllele')
+    print(f"{variant}: p={pvalue}, risk allele={risk_allele}")
+```
+
+**Example 2: Get variant information and all trait associations**
+```python
+import requests
+
+variant = "rs7903146"
+base_url = "https://www.ebi.ac.uk/gwas/rest/api"
+
+# Get variant details
+url = f"{base_url}/singleNucleotidePolymorphisms/{variant}"
+response = requests.get(url, headers={"Content-Type": "application/json"})
+variant_data = response.json()
+
+# Get all associations for this variant
+url = f"{base_url}/singleNucleotidePolymorphisms/{variant}/associations"
+params = {"projection": "associationBySnp"}
+response = requests.get(url, params=params, headers={"Content-Type": "application/json"})
+associations = response.json()
+
+# Extract trait names and p-values
+for assoc in associations.get('_embedded', {}).get('associations', []):
+    trait = assoc.get('efoTrait')
+    pvalue = assoc.get('pvalue')
+    print(f"Trait: {trait}, p-value: {pvalue}")
+```
+
+**Example 3: Access summary statistics**
+```python
+import requests
+
+# Query summary statistics API
+base_url = "https://www.ebi.ac.uk/gwas/summary-statistics/api"
+
+# Find associations by trait with p-value threshold
+trait = "EFO_0001360"  # Type 2 diabetes
+p_upper = "0.000000001"  # p < 1e-9
+url = f"{base_url}/traits/{trait}/associations"
+params = {
+    "p_upper": p_upper,
+    "size": 100  # Number of results
+}
+response = requests.get(url, params=params)
+results = response.json()
+
+# Process genome-wide significant hits
+for hit in results.get('_embedded', {}).get('associations', []):
+    variant_id = hit.get('variant_id')
+    chromosome = hit.get('chromosome')
+    position = hit.get('base_pair_location')
+    pvalue = hit.get('p_value')
+    print(f"{chromosome}:{position} ({variant_id}): p={pvalue}")
+```
+
+**Example 4: Query by chromosomal region**
+```python
+import requests
+
+# Find variants in a specific genomic region
+chromosome = "10"
+start_pos = 114000000
+end_pos = 115000000
+
+base_url = "https://www.ebi.ac.uk/gwas/rest/api"
+url = f"{base_url}/singleNucleotidePolymorphisms/search/findByChromBpLocationRange"
+params = {
+    "chrom": chromosome,
+    "bpStart": start_pos,
+    "bpEnd": end_pos
+}
+response = requests.get(url, params=params, headers={"Content-Type": "application/json"})
+variants_in_region = response.json()
+```
+
+### 5. Working with Summary Statistics
+
+The GWAS Catalog hosts full summary statistics for many studies, providing access to all tested variants (not just genome-wide significant hits).
+
+**Access Methods:**
+1. **FTP download**: http://ftp.ebi.ac.uk/pub/databases/gwas/summary_statistics/
+2. **REST API**: Query-based access to summary statistics
+3. **Web interface**: Browse and download via the website
+
+**Summary Statistics API Features:**
+- Filter by chromosome, position, p-value
+- Query specific variants across studies
+- Retrieve effect sizes and allele frequencies
+- Access harmonized and standardized data
+
+**Example: Download summary statistics for a study**
+```python
+import requests
+import gzip
+
+# Get available summary statistics
+base_url = "https://www.ebi.ac.uk/gwas/summary-statistics/api"
+url = f"{base_url}/studies/GCST001234"
+response = requests.get(url)
+study_info = response.json()
+
+# Download link is provided in the response
+# Alternatively, use FTP:
+# ftp://ftp.ebi.ac.uk/pub/databases/gwas/summary_statistics/GCSTXXXXXX/
+```
+
+### 6. Data Integration and Cross-referencing
+
+The GWAS Catalog provides links to external resources:
+
+**Genomic Databases:**
+- Ensembl: Gene annotations and variant consequences
+- dbSNP: Variant identifiers and population frequencies
+- gnomAD: Population allele frequencies
+
+**Functional Resources:**
+- Open Targets: Target-disease associations
+- PGS Catalog: Polygenic risk scores
+- UCSC Genome Browser: Genomic context
+
+**Phenotype Resources:**
+- EFO (Experimental Factor Ontology): Standardized trait terms
+- OMIM: Disease gene relationships
+- Disease Ontology: Disease hierarchies
+
+**Following Links in API Responses:**
+```python
+import requests
+
+# API responses include _links for related resources
+response = requests.get("https://www.ebi.ac.uk/gwas/rest/api/studies/GCST001234")
+study = response.json()
+
+# Follow link to associations
+associations_url = study['_links']['associations']['href']
+associations_response = requests.get(associations_url)
+```
+
+## Query Workflows
+
+### Workflow 1: Exploring Genetic Associations for a Disease
+
+1. **Identify the trait** using EFO terms or free text:
+   - Search web interface for disease name
+   - Note the EFO ID (e.g., EFO_0001360 for type 2 diabetes)
+
+2. **Query associations via API:**
+   ```python
+   url = f"https://www.ebi.ac.uk/gwas/rest/api/efoTraits/{efo_id}/associations"
+   ```
+
+3. **Filter by significance and population:**
+   - Check p-values (genome-wide significant: p ≤ 5×10⁻⁸)
+   - Review ancestry information in study metadata
+   - Filter by sample size or discovery/replication status
+
+4. **Extract variant details:**
+   - rs IDs for each association
+   - Effect alleles and directions
+   - Effect sizes (odds ratios, beta coefficients)
+   - Population allele frequencies
+
+5. **Cross-reference with other databases:**
+   - Look up variant consequences in Ensembl
+   - Check population frequencies in gnomAD
+   - Explore gene function and pathways
+
+### Workflow 2: Investigating a Specific Genetic Variant
+
+1. **Query the variant:**
+   ```python
+   url = f"https://www.ebi.ac.uk/gwas/rest/api/singleNucleotidePolymorphisms/{rs_id}"
+   ```
+
+2. **Retrieve all trait associations:**
+   ```python
+   url = f"https://www.ebi.ac.uk/gwas/rest/api/singleNucleotidePolymorphisms/{rs_id}/associations"
+   ```
+
+3. **Analyze pleiotropy:**
+   - Identify all traits associated with this variant
+   - Review effect directions across traits
+   - Look for shared biological pathways
+
+4. **Check genomic context:**
+   - Determine nearby genes
+   - Identify if variant is in coding/regulatory regions
+   - Review linkage disequilibrium with other variants
+
+### Workflow 3: Gene-Centric Association Analysis
+
+1. **Search by gene symbol** in web interface or:
+   ```python
+   url = f"https://www.ebi.ac.uk/gwas/rest/api/singleNucleotidePolymorphisms/search/findByGene"
+   params = {"geneName": gene_symbol}
+   ```
+
+2. **Retrieve variants in gene region:**
+   - Get chromosomal coordinates for gene
+   - Query variants in region
+   - Include promoter and regulatory regions (extend boundaries)
+
+3. **Analyze association patterns:**
+   - Identify traits associated with variants in this gene
+   - Look for consistent associations across studies
+   - Review effect sizes and directions
+
+4. **Functional interpretation:**
+   - Determine variant consequences (missense, regulatory, etc.)
+   - Check expression QTL (eQTL) data
+   - Review pathway and network context
+
+### Workflow 4: Systematic Review of Genetic Evidence
+
+1. **Define research question:**
+   - Specific trait or disease of interest
+   - Population considerations
+   - Study design requirements
+
+2. **Comprehensive variant extraction:**
+   - Query all associations for trait
+   - Set significance threshold
+   - Note discovery and replication studies
+
+3. **Quality assessment:**
+   - Review study sample sizes
+   - Check for population diversity
+   - Assess heterogeneity across studies
+   - Identify potential biases
+
+4. **Data synthesis:**
+   - Aggregate associations across studies
+   - Perform meta-analysis if applicable
+   - Create summary tables
+   - Generate Manhattan or forest plots
+
+5. **Export and documentation:**
+   - Download full association data
+   - Export summary statistics if needed
+   - Document search strategy and date
+   - Create reproducible analysis scripts
+
+### Workflow 5: Accessing and Analyzing Summary Statistics
+
+1. **Identify studies with summary statistics:**
+   - Browse summary statistics portal
+   - Check FTP directory listings
+   - Query API for available studies
+
+2. **Download summary statistics:**
+   ```bash
+   # Via FTP
+   wget ftp://ftp.ebi.ac.uk/pub/databases/gwas/summary_statistics/GCSTXXXXXX/harmonised/GCSTXXXXXX-harmonised.tsv.gz
+   ```
+
+3. **Query via API for specific variants:**
+   ```python
+   url = f"https://www.ebi.ac.uk/gwas/summary-statistics/api/chromosomes/{chrom}/associations"
+   params = {"start": start_pos, "end": end_pos}
+   ```
+
+4. **Process and analyze:**
+   - Filter by p-value thresholds
+   - Extract effect sizes and confidence intervals
+   - Perform downstream analyses (fine-mapping, colocalization, etc.)
+
+## Response Formats and Data Fields
+
+**Key Fields in Association Records:**
+- `rsId`: Variant identifier (rs number)
+- `strongestAllele`: Risk allele for the association
+- `pvalue`: Association p-value
+- `pvalueText`: P-value as text (may include inequality)
+- `orPerCopyNum`: Odds ratio or beta coefficient
+- `betaNum`: Effect size (for quantitative traits)
+- `betaUnit`: Unit of measurement for beta
+- `range`: Confidence interval
+- `efoTrait`: Associated trait name
+- `mappedLabel`: EFO-mapped trait term
+
+**Study Metadata Fields:**
+- `accessionId`: GCST study identifier
+- `pubmedId`: PubMed ID
+- `author`: First author
+- `publicationDate`: Publication date
+- `ancestryInitial`: Discovery population ancestry
+- `ancestryReplication`: Replication population ancestry
+- `sampleSize`: Total sample size
+
+**Pagination:**
+Results are paginated (default 20 items per page). Navigate using:
+- `size` parameter: Number of results per page
+- `page` parameter: Page number (0-indexed)
+- `_links` in response: URLs for next/previous pages
+
+## Best Practices
+
+### Query Strategy
+- Start with web interface to identify relevant EFO terms and study accessions
+- Use API for bulk data extraction and automated analyses
+- Implement pagination handling for large result sets
+- Cache API responses to minimize redundant requests
+
+### Data Interpretation
+- Always check p-value thresholds (genome-wide: 5×10⁻⁸)
+- Review ancestry information for population applicability
+- Consider sample size when assessing evidence strength
+- Check for replication across independent studies
+- Be aware of winner's curse in effect size estimates
+
+### Rate Limiting and Ethics
+- Respect API usage guidelines (no excessive requests)
+- Use summary statistics downloads for genome-wide analyses
+- Implement appropriate delays between API calls
+- Cache results locally when performing iterative analyses
+- Cite the GWAS Catalog in publications
+
+### Data Quality Considerations
+- GWAS Catalog curates published associations (may contain inconsistencies)
+- Effect sizes reported as published (may need harmonization)
+- Some studies report conditional or joint associations
+- Check for study overlap when combining results
+- Be aware of ascertainment and selection biases
+
+## Python Integration Example
+
+Complete workflow for querying and analyzing GWAS data:
+
+```python
+import requests
+import pandas as pd
+from time import sleep
+
+def query_gwas_catalog(trait_id, p_threshold=5e-8):
+    """
+    Query GWAS Catalog for trait associations
+
+    Args:
+        trait_id: EFO trait identifier (e.g., 'EFO_0001360')
+        p_threshold: P-value threshold for filtering
+
+    Returns:
+        pandas DataFrame with association results
+    """
+    base_url = "https://www.ebi.ac.uk/gwas/rest/api"
+    url = f"{base_url}/efoTraits/{trait_id}/associations"
+
+    headers = {"Content-Type": "application/json"}
+    results = []
+    page = 0
+
+    while True:
+        params = {"page": page, "size": 100}
+        response = requests.get(url, params=params, headers=headers)
+
+        if response.status_code != 200:
+            break
+
+        data = response.json()
+        associations = data.get('_embedded', {}).get('associations', [])
+
+        if not associations:
+            break
+
+        for assoc in associations:
+            pvalue = assoc.get('pvalue')
+            if pvalue and float(pvalue) <= p_threshold:
+                results.append({
+                    'variant': assoc.get('rsId'),
+                    'pvalue': pvalue,
+                    'risk_allele': assoc.get('strongestAllele'),
+                    'or_beta': assoc.get('orPerCopyNum') or assoc.get('betaNum'),
+                    'trait': assoc.get('efoTrait'),
+                    'pubmed_id': assoc.get('pubmedId')
+                })
+
+        page += 1
+        sleep(0.1)  # Rate limiting
+
+    return pd.DataFrame(results)
+
+# Example usage
+df = query_gwas_catalog('EFO_0001360')  # Type 2 diabetes
+print(df.head())
+print(f"\nTotal associations: {len(df)}")
+print(f"Unique variants: {df['variant'].nunique()}")
+```
+
+## Resources
+
+### references/api_reference.md
+
+Comprehensive API documentation including:
+- Detailed endpoint specifications for both APIs
+- Complete list of query parameters and filters
+- Response format specifications and field descriptions
+- Advanced query examples and patterns
+- Error handling and troubleshooting
+- Integration with external databases
+
+Consult this reference when:
+- Constructing complex API queries
+- Understanding response structures
+- Implementing pagination or batch operations
+- Troubleshooting API errors
+- Exploring advanced filtering options
+
+### Training Materials
+
+The GWAS Catalog team provides workshop materials:
+- GitHub repository: https://github.com/EBISPOT/GWAS_Catalog-workshop
+- Jupyter notebooks with example queries
+- Google Colab integration for cloud execution
+
+## Important Notes
+
+### Data Updates
+- The GWAS Catalog is updated regularly with new publications
+- Re-run queries periodically for comprehensive coverage
+- Summary statistics are added as studies release data
+- EFO mappings may be updated over time
+
+### Citation Requirements
+When using GWAS Catalog data, cite:
+- Sollis E, et al. (2023) The NHGRI-EBI GWAS Catalog: knowledgebase and deposition resource. Nucleic Acids Research. PMID: 37953337
+- Include access date and version when available
+- Cite original studies when discussing specific findings
+
+### Limitations
+- Not all GWAS publications are included (curation criteria apply)
+- Full summary statistics available for subset of studies
+- Effect sizes may require harmonization across studies
+- Population diversity is growing but historically limited
+- Some associations represent conditional or joint effects
+
+### Data Access
+- Web interface: Free, no registration required
+- REST APIs: Free, no API key needed
+- FTP downloads: Open access
+- Rate limiting applies to API (be respectful)
+
+## Additional Resources
+
+- **GWAS Catalog website**: https://www.ebi.ac.uk/gwas/
+- **Documentation**: https://www.ebi.ac.uk/gwas/docs
+- **API documentation**: https://www.ebi.ac.uk/gwas/rest/docs/api
+- **Summary Statistics API**: https://www.ebi.ac.uk/gwas/summary-statistics/docs/
+- **FTP site**: http://ftp.ebi.ac.uk/pub/databases/gwas/
+- **Training materials**: https://github.com/EBISPOT/GWAS_Catalog-workshop
+- **PGS Catalog** (polygenic scores): https://www.pgscatalog.org/
+- **Help and support**: gwas-info@ebi.ac.uk
diff --git a/scientific-databases/gwas-database/references/api_reference.md b/scientific-databases/gwas-database/references/api_reference.md
new file mode 100644
index 0000000..c5b9446
--- /dev/null
+++ b/scientific-databases/gwas-database/references/api_reference.md
@@ -0,0 +1,793 @@
+# GWAS Catalog API Reference
+
+Comprehensive reference for the GWAS Catalog REST APIs, including endpoint specifications, query parameters, response formats, and advanced usage patterns.
+
+## Table of Contents
+
+- [API Overview](#api-overview)
+- [Authentication and Rate Limiting](#authentication-and-rate-limiting)
+- [GWAS Catalog REST API](#gwas-catalog-rest-api)
+- [Summary Statistics API](#summary-statistics-api)
+- [Response Formats](#response-formats)
+- [Error Handling](#error-handling)
+- [Advanced Query Patterns](#advanced-query-patterns)
+- [Integration Examples](#integration-examples)
+
+## API Overview
+
+The GWAS Catalog provides two complementary REST APIs:
+
+1. **GWAS Catalog REST API**: Access to curated SNP-trait associations, studies, and metadata
+2. **Summary Statistics API**: Access to full GWAS summary statistics (all tested variants)
+
+Both APIs use RESTful design principles with JSON responses in HAL (Hypertext Application Language) format, which includes `_links` for resource navigation.
+
+### Base URLs
+
+```
+GWAS Catalog API:         https://www.ebi.ac.uk/gwas/rest/api
+Summary Statistics API:   https://www.ebi.ac.uk/gwas/summary-statistics/api
+```
+
+### Version Information
+
+The GWAS Catalog REST API v2.0 was released in 2024, with significant improvements:
+- New endpoints (publications, genes, genomic context, ancestries)
+- Enhanced data exposure (cohorts, background traits, licenses)
+- Improved query capabilities
+- Better performance and documentation
+
+The previous API version remains available until May 2026 for backward compatibility.
+
+## Authentication and Rate Limiting
+
+### Authentication
+
+**No authentication required** - Both APIs are open access and do not require API keys or registration.
+
+### Rate Limiting
+
+While no explicit rate limits are documented, follow best practices:
+- Implement delays between consecutive requests (e.g., 0.1-0.5 seconds)
+- Use pagination for large result sets
+- Cache responses locally
+- Use bulk downloads (FTP) for genome-wide data
+- Avoid hammering the API with rapid consecutive requests
+
+**Example with rate limiting:**
+```python
+import requests
+from time import sleep
+
+def query_with_rate_limit(url, delay=0.1):
+    response = requests.get(url)
+    sleep(delay)
+    return response.json()
+```
+
+## GWAS Catalog REST API
+
+The main API provides access to curated GWAS associations, studies, variants, and traits.
+
+### Core Endpoints
+
+#### 1. Studies
+
+**Get all studies:**
+```
+GET /studies
+```
+
+**Get specific study:**
+```
+GET /studies/{accessionId}
+```
+
+**Search studies:**
+```
+GET /studies/search/findByPublicationIdPubmedId?pubmedId={pmid}
+GET /studies/search/findByDiseaseTrait?diseaseTrait={trait}
+```
+
+**Query Parameters:**
+- `page`: Page number (0-indexed)
+- `size`: Results per page (default: 20)
+- `sort`: Sort field (e.g., `publicationDate,desc`)
+
+**Example:**
+```python
+import requests
+
+# Get a specific study
+url = "https://www.ebi.ac.uk/gwas/rest/api/studies/GCST001795"
+response = requests.get(url, headers={"Content-Type": "application/json"})
+study = response.json()
+
+print(f"Title: {study.get('title')}")
+print(f"PMID: {study.get('publicationInfo', {}).get('pubmedId')}")
+print(f"Sample size: {study.get('initialSampleSize')}")
+```
+
+**Response Fields:**
+- `accessionId`: Study identifier (GCST ID)
+- `title`: Study title
+- `publicationInfo`: Publication details including PMID
+- `initialSampleSize`: Discovery cohort description
+- `replicationSampleSize`: Replication cohort description
+- `ancestries`: Population ancestry information
+- `genotypingTechnologies`: Array or sequencing platforms
+- `_links`: Links to related resources
+
+#### 2. Associations
+
+**Get all associations:**
+```
+GET /associations
+```
+
+**Get specific association:**
+```
+GET /associations/{associationId}
+```
+
+**Get associations for a trait:**
+```
+GET /efoTraits/{efoId}/associations
+```
+
+**Get associations for a variant:**
+```
+GET /singleNucleotidePolymorphisms/{rsId}/associations
+```
+
+**Query Parameters:**
+- `projection`: Response projection (e.g., `associationBySnp`)
+- `page`, `size`, `sort`: Pagination controls
+
+**Example:**
+```python
+import requests
+
+# Find all associations for type 2 diabetes
+trait_id = "EFO_0001360"
+url = f"https://www.ebi.ac.uk/gwas/rest/api/efoTraits/{trait_id}/associations"
+params = {"size": 100, "page": 0}
+response = requests.get(url, params=params, headers={"Content-Type": "application/json"})
+data = response.json()
+
+associations = data.get('_embedded', {}).get('associations', [])
+print(f"Found {len(associations)} associations")
+```
+
+**Response Fields:**
+- `rsId`: Variant identifier
+- `strongestAllele`: Risk or effect allele
+- `pvalue`: Association p-value
+- `pvalueText`: P-value as reported (may include inequality)
+- `pvalueMantissa`: Mantissa of p-value
+- `pvalueExponent`: Exponent of p-value
+- `orPerCopyNum`: Odds ratio per allele copy
+- `betaNum`: Effect size (quantitative traits)
+- `betaUnit`: Unit of measurement
+- `range`: Confidence interval
+- `standardError`: Standard error
+- `efoTrait`: Trait name
+- `mappedLabel`: EFO standardized term
+- `studyId`: Associated study accession
+
+#### 3. Variants (Single Nucleotide Polymorphisms)
+
+**Get variant details:**
+```
+GET /singleNucleotidePolymorphisms/{rsId}
+```
+
+**Search variants:**
+```
+GET /singleNucleotidePolymorphisms/search/findByRsId?rsId={rsId}
+GET /singleNucleotidePolymorphisms/search/findByChromBpLocationRange?chrom={chr}&bpStart={start}&bpEnd={end}
+GET /singleNucleotidePolymorphisms/search/findByGene?geneName={gene}
+```
+
+**Example:**
+```python
+import requests
+
+# Get variant information
+rs_id = "rs7903146"
+url = f"https://www.ebi.ac.uk/gwas/rest/api/singleNucleotidePolymorphisms/{rs_id}"
+response = requests.get(url, headers={"Content-Type": "application/json"})
+variant = response.json()
+
+print(f"rsID: {variant.get('rsId')}")
+print(f"Location: chr{variant.get('locations', [{}])[0].get('chromosomeName')}:{variant.get('locations', [{}])[0].get('chromosomePosition')}")
+```
+
+**Response Fields:**
+- `rsId`: rs number
+- `merged`: Indicates if variant merged with another
+- `functionalClass`: Variant consequence
+- `locations`: Array of genomic locations
+  - `chromosomeName`: Chromosome number
+  - `chromosomePosition`: Base pair position
+  - `region`: Genomic region information
+- `genomicContexts`: Nearby genes
+- `lastUpdateDate`: Last modification date
+
+#### 4. Traits (EFO Terms)
+
+**Get trait information:**
+```
+GET /efoTraits/{efoId}
+```
+
+**Search traits:**
+```
+GET /efoTraits/search/findByEfoUri?uri={efoUri}
+GET /efoTraits/search/findByTraitIgnoreCase?trait={traitName}
+```
+
+**Example:**
+```python
+import requests
+
+# Get trait details
+trait_id = "EFO_0001360"
+url = f"https://www.ebi.ac.uk/gwas/rest/api/efoTraits/{trait_id}"
+response = requests.get(url, headers={"Content-Type": "application/json"})
+trait = response.json()
+
+print(f"Trait: {trait.get('trait')}")
+print(f"EFO URI: {trait.get('uri')}")
+```
+
+#### 5. Publications
+
+**Get publication information:**
+```
+GET /publications
+GET /publications/{publicationId}
+GET /publications/search/findByPubmedId?pubmedId={pmid}
+```
+
+#### 6. Genes
+
+**Get gene information:**
+```
+GET /genes
+GET /genes/{geneId}
+GET /genes/search/findByGeneName?geneName={symbol}
+```
+
+### Pagination and Navigation
+
+All list endpoints support pagination:
+
+```python
+import requests
+
+def get_all_associations(trait_id):
+    """Retrieve all associations for a trait with pagination"""
+    base_url = "https://www.ebi.ac.uk/gwas/rest/api"
+    url = f"{base_url}/efoTraits/{trait_id}/associations"
+    all_associations = []
+    page = 0
+
+    while True:
+        params = {"page": page, "size": 100}
+        response = requests.get(url, params=params, headers={"Content-Type": "application/json"})
+
+        if response.status_code != 200:
+            break
+
+        data = response.json()
+        associations = data.get('_embedded', {}).get('associations', [])
+
+        if not associations:
+            break
+
+        all_associations.extend(associations)
+        page += 1
+
+    return all_associations
+```
+
+### HAL Links
+
+Responses include `_links` for resource navigation:
+
+```python
+import requests
+
+# Get study and follow links to associations
+response = requests.get("https://www.ebi.ac.uk/gwas/rest/api/studies/GCST001795")
+study = response.json()
+
+# Follow link to associations
+associations_url = study['_links']['associations']['href']
+associations_response = requests.get(associations_url)
+associations = associations_response.json()
+```
+
+## Summary Statistics API
+
+Access full GWAS summary statistics for studies that have deposited complete data.
+
+### Base URL
+```
+https://www.ebi.ac.uk/gwas/summary-statistics/api
+```
+
+### Core Endpoints
+
+#### 1. Studies
+
+**Get all studies with summary statistics:**
+```
+GET /studies
+```
+
+**Get specific study:**
+```
+GET /studies/{gcstId}
+```
+
+#### 2. Traits
+
+**Get trait information:**
+```
+GET /traits/{efoId}
+```
+
+**Get associations for a trait:**
+```
+GET /traits/{efoId}/associations
+```
+
+**Query Parameters:**
+- `p_lower`: Lower p-value threshold
+- `p_upper`: Upper p-value threshold
+- `size`: Number of results
+- `page`: Page number
+
+**Example:**
+```python
+import requests
+
+# Find highly significant associations for a trait
+trait_id = "EFO_0001360"
+base_url = "https://www.ebi.ac.uk/gwas/summary-statistics/api"
+url = f"{base_url}/traits/{trait_id}/associations"
+params = {
+    "p_upper": "0.000000001",  # p < 1e-9
+    "size": 100
+}
+response = requests.get(url, params=params)
+results = response.json()
+```
+
+#### 3. Chromosomes
+
+**Get associations by chromosome:**
+```
+GET /chromosomes/{chromosome}/associations
+```
+
+**Query by genomic region:**
+```
+GET /chromosomes/{chromosome}/associations?start={start}&end={end}
+```
+
+**Example:**
+```python
+import requests
+
+# Query variants in a specific region
+chromosome = "10"
+start_pos = 114000000
+end_pos = 115000000
+
+base_url = "https://www.ebi.ac.uk/gwas/summary-statistics/api"
+url = f"{base_url}/chromosomes/{chromosome}/associations"
+params = {
+    "start": start_pos,
+    "end": end_pos,
+    "size": 1000
+}
+response = requests.get(url, params=params)
+variants = response.json()
+```
+
+#### 4. Variants
+
+**Get specific variant across studies:**
+```
+GET /variants/{variantId}
+```
+
+**Search by variant ID:**
+```
+GET /variants/{variantId}/associations
+```
+
+### Response Fields
+
+**Association Fields:**
+- `variant_id`: Variant identifier
+- `chromosome`: Chromosome number
+- `base_pair_location`: Position (bp)
+- `effect_allele`: Effect allele
+- `other_allele`: Reference allele
+- `effect_allele_frequency`: Allele frequency
+- `beta`: Effect size
+- `standard_error`: Standard error
+- `p_value`: P-value
+- `ci_lower`: Lower confidence interval
+- `ci_upper`: Upper confidence interval
+- `odds_ratio`: Odds ratio (case-control studies)
+- `study_accession`: GCST ID
+
+## Response Formats
+
+### Content Type
+
+All API requests should include the header:
+```
+Content-Type: application/json
+```
+
+### HAL Format
+
+Responses follow the HAL (Hypertext Application Language) specification:
+
+```json
+{
+  "_embedded": {
+    "associations": [
+      {
+        "rsId": "rs7903146",
+        "pvalue": 1.2e-30,
+        "efoTrait": "type 2 diabetes",
+        "_links": {
+          "self": {
+            "href": "https://www.ebi.ac.uk/gwas/rest/api/associations/12345"
+          }
+        }
+      }
+    ]
+  },
+  "_links": {
+    "self": {
+      "href": "https://www.ebi.ac.uk/gwas/rest/api/efoTraits/EFO_0001360/associations?page=0"
+    },
+    "next": {
+      "href": "https://www.ebi.ac.uk/gwas/rest/api/efoTraits/EFO_0001360/associations?page=1"
+    }
+  },
+  "page": {
+    "size": 20,
+    "totalElements": 1523,
+    "totalPages": 77,
+    "number": 0
+  }
+}
+```
+
+### Page Metadata
+
+Paginated responses include page information:
+- `size`: Items per page
+- `totalElements`: Total number of results
+- `totalPages`: Total number of pages
+- `number`: Current page number (0-indexed)
+
+## Error Handling
+
+### HTTP Status Codes
+
+- `200 OK`: Successful request
+- `400 Bad Request`: Invalid parameters
+- `404 Not Found`: Resource not found
+- `500 Internal Server Error`: Server error
+
+### Error Response Format
+
+```json
+{
+  "timestamp": "2025-10-19T12:00:00.000+00:00",
+  "status": 404,
+  "error": "Not Found",
+  "message": "No association found with id: 12345",
+  "path": "/gwas/rest/api/associations/12345"
+}
+```
+
+### Error Handling Example
+
+```python
+import requests
+
+def safe_api_request(url, params=None):
+    """Make API request with error handling"""
+    try:
+        response = requests.get(url, params=params, timeout=30)
+        response.raise_for_status()
+        return response.json()
+    except requests.exceptions.HTTPError as e:
+        print(f"HTTP Error: {e}")
+        print(f"Response: {response.text}")
+        return None
+    except requests.exceptions.ConnectionError:
+        print("Connection error - check network")
+        return None
+    except requests.exceptions.Timeout:
+        print("Request timed out")
+        return None
+    except requests.exceptions.RequestException as e:
+        print(f"Request error: {e}")
+        return None
+```
+
+## Advanced Query Patterns
+
+### 1. Cross-referencing Variants and Traits
+
+```python
+import requests
+
+def get_variant_pleiotropy(rs_id):
+    """Get all traits associated with a variant"""
+    base_url = "https://www.ebi.ac.uk/gwas/rest/api"
+    url = f"{base_url}/singleNucleotidePolymorphisms/{rs_id}/associations"
+    params = {"projection": "associationBySnp"}
+
+    response = requests.get(url, params=params, headers={"Content-Type": "application/json"})
+    data = response.json()
+
+    traits = {}
+    for assoc in data.get('_embedded', {}).get('associations', []):
+        trait = assoc.get('efoTrait')
+        pvalue = assoc.get('pvalue')
+        if trait:
+            if trait not in traits or float(pvalue) < float(traits[trait]):
+                traits[trait] = pvalue
+
+    return traits
+
+# Example usage
+pleiotropy = get_variant_pleiotropy('rs7903146')
+for trait, pval in sorted(pleiotropy.items(), key=lambda x: float(x[1])):
+    print(f"{trait}: p={pval}")
+```
+
+### 2. Filtering by P-value Threshold
+
+```python
+import requests
+
+def get_significant_associations(trait_id, p_threshold=5e-8):
+    """Get genome-wide significant associations"""
+    base_url = "https://www.ebi.ac.uk/gwas/rest/api"
+    url = f"{base_url}/efoTraits/{trait_id}/associations"
+
+    results = []
+    page = 0
+
+    while True:
+        params = {"page": page, "size": 100}
+        response = requests.get(url, params=params, headers={"Content-Type": "application/json"})
+
+        if response.status_code != 200:
+            break
+
+        data = response.json()
+        associations = data.get('_embedded', {}).get('associations', [])
+
+        if not associations:
+            break
+
+        for assoc in associations:
+            pvalue = assoc.get('pvalue')
+            if pvalue and float(pvalue) <= p_threshold:
+                results.append(assoc)
+
+        page += 1
+
+    return results
+```
+
+### 3. Combining Main and Summary Statistics APIs
+
+```python
+import requests
+
+def get_complete_variant_data(rs_id):
+    """Get variant data from both APIs"""
+    main_url = f"https://www.ebi.ac.uk/gwas/rest/api/singleNucleotidePolymorphisms/{rs_id}"
+
+    # Get basic variant info
+    response = requests.get(main_url, headers={"Content-Type": "application/json"})
+    variant_info = response.json()
+
+    # Get associations
+    assoc_url = f"{main_url}/associations"
+    response = requests.get(assoc_url, headers={"Content-Type": "application/json"})
+    associations = response.json()
+
+    # Could also query summary statistics API for this variant
+    # across all studies with summary data
+
+    return {
+        "variant": variant_info,
+        "associations": associations
+    }
+```
+
+### 4. Genomic Region Queries
+
+```python
+import requests
+
+def query_region(chromosome, start, end, p_threshold=None):
+    """Query variants in genomic region"""
+    # From main API
+    base_url = "https://www.ebi.ac.uk/gwas/rest/api"
+    url = f"{base_url}/singleNucleotidePolymorphisms/search/findByChromBpLocationRange"
+    params = {
+        "chrom": chromosome,
+        "bpStart": start,
+        "bpEnd": end,
+        "size": 1000
+    }
+
+    response = requests.get(url, params=params, headers={"Content-Type": "application/json"})
+    variants = response.json()
+
+    # Can also query summary statistics API
+    sumstats_url = f"https://www.ebi.ac.uk/gwas/summary-statistics/api/chromosomes/{chromosome}/associations"
+    sumstats_params = {"start": start, "end": end, "size": 1000}
+    if p_threshold:
+        sumstats_params["p_upper"] = str(p_threshold)
+
+    sumstats_response = requests.get(sumstats_url, params=sumstats_params)
+    sumstats = sumstats_response.json()
+
+    return {
+        "catalog_variants": variants,
+        "summary_stats": sumstats
+    }
+```
+
+## Integration Examples
+
+### Complete Workflow: Disease Genetic Architecture
+
+```python
+import requests
+import pandas as pd
+from time import sleep
+
+class GWASCatalogQuery:
+    def __init__(self):
+        self.base_url = "https://www.ebi.ac.uk/gwas/rest/api"
+        self.headers = {"Content-Type": "application/json"}
+
+    def get_trait_associations(self, trait_id, p_threshold=5e-8):
+        """Get all associations for a trait"""
+        url = f"{self.base_url}/efoTraits/{trait_id}/associations"
+        results = []
+        page = 0
+
+        while True:
+            params = {"page": page, "size": 100}
+            response = requests.get(url, params=params, headers=self.headers)
+
+            if response.status_code != 200:
+                break
+
+            data = response.json()
+            associations = data.get('_embedded', {}).get('associations', [])
+
+            if not associations:
+                break
+
+            for assoc in associations:
+                pvalue = assoc.get('pvalue')
+                if pvalue and float(pvalue) <= p_threshold:
+                    results.append({
+                        'rs_id': assoc.get('rsId'),
+                        'pvalue': float(pvalue),
+                        'risk_allele': assoc.get('strongestAllele'),
+                        'or_beta': assoc.get('orPerCopyNum') or assoc.get('betaNum'),
+                        'study': assoc.get('studyId'),
+                        'pubmed_id': assoc.get('pubmedId')
+                    })
+
+            page += 1
+            sleep(0.1)
+
+        return pd.DataFrame(results)
+
+    def get_variant_details(self, rs_id):
+        """Get detailed variant information"""
+        url = f"{self.base_url}/singleNucleotidePolymorphisms/{rs_id}"
+        response = requests.get(url, headers=self.headers)
+
+        if response.status_code == 200:
+            return response.json()
+        return None
+
+    def get_gene_associations(self, gene_name):
+        """Get variants associated with a gene"""
+        url = f"{self.base_url}/singleNucleotidePolymorphisms/search/findByGene"
+        params = {"geneName": gene_name}
+        response = requests.get(url, params=params, headers=self.headers)
+
+        if response.status_code == 200:
+            return response.json()
+        return None
+
+# Example usage
+gwas = GWASCatalogQuery()
+
+# Query type 2 diabetes associations
+df = gwas.get_trait_associations('EFO_0001360')
+print(f"Found {len(df)} genome-wide significant associations")
+print(f"Unique variants: {df['rs_id'].nunique()}")
+
+# Get top variants
+top_variants = df.nsmallest(10, 'pvalue')
+print("\nTop 10 variants:")
+print(top_variants[['rs_id', 'pvalue', 'risk_allele']])
+
+# Get details for top variant
+if len(top_variants) > 0:
+    top_rs = top_variants.iloc[0]['rs_id']
+    variant_info = gwas.get_variant_details(top_rs)
+    if variant_info:
+        loc = variant_info.get('locations', [{}])[0]
+        print(f"\n{top_rs} location: chr{loc.get('chromosomeName')}:{loc.get('chromosomePosition')}")
+```
+
+### FTP Download Integration
+
+```python
+import requests
+from pathlib import Path
+
+def download_summary_statistics(gcst_id, output_dir="."):
+    """Download summary statistics from FTP"""
+    # FTP URL pattern
+    ftp_base = "http://ftp.ebi.ac.uk/pub/databases/gwas/summary_statistics"
+
+    # Try harmonised file first
+    harmonised_url = f"{ftp_base}/{gcst_id}/harmonised/{gcst_id}-harmonised.tsv.gz"
+
+    output_path = Path(output_dir) / f"{gcst_id}.tsv.gz"
+
+    try:
+        response = requests.get(harmonised_url, stream=True)
+        response.raise_for_status()
+
+        with open(output_path, 'wb') as f:
+            for chunk in response.iter_content(chunk_size=8192):
+                f.write(chunk)
+
+        print(f"Downloaded {gcst_id} to {output_path}")
+        return output_path
+
+    except requests.exceptions.HTTPError:
+        print(f"Harmonised file not found for {gcst_id}")
+        return None
+
+# Example usage
+download_summary_statistics("GCST001234", output_dir="./sumstats")
+```
+
+## Additional Resources
+
+- **Interactive API Documentation**: https://www.ebi.ac.uk/gwas/rest/docs/api
+- **Summary Statistics API Docs**: https://www.ebi.ac.uk/gwas/summary-statistics/docs/
+- **Workshop Materials**: https://github.com/EBISPOT/GWAS_Catalog-workshop
+- **Blog Post on API v2**: https://ebispot.github.io/gwas-blog/rest-api-v2-release/
+- **R Package (gwasrapidd)**: https://cran.r-project.org/package=gwasrapidd