Ensembl REST API
Ensembl REST API provides programmatic access to the Ensembl genome browser database, covering gene annotations, sequence retrieval, variant data, comparative genomics, and phenotype associations for 200+ species.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
No authentication — public scientific data. TLS enforced. No sensitive data exposure risk. Rate limiting prevents abuse.
⚡ Reliability
Best When
Building agents that need rich genome annotation, cross-species comparison, or variant consequence prediction with stable versioned Ensembl IDs and a well-documented Swagger interface.
Avoid When
You need NCBI RefSeq accessions as primary identifiers — Ensembl and RefSeq IDs require mapping. Use NCBI E-utilities if RefSeq is your primary system.
Use Cases
- • Gene lookup agents resolving gene symbols to Ensembl IDs and retrieving stable annotations across species
- • Variant effect prediction pipelines using the VEP endpoint to annotate genomic variants with functional consequences
- • Comparative genomics agents finding orthologs and paralogs across human, mouse, zebrafish, and other model organisms
- • Sequence retrieval workflows fetching genomic, cDNA, or protein sequences by coordinates or Ensembl ID
- • Phenotype association queries linking genes to OMIM, ClinVar, and GWAS phenotypes via the phenotype endpoint
Not For
- • Applications requiring the very latest genome assemblies — Ensembl releases are versioned and lag bleeding-edge updates
- • Non-Ensembl genome databases (UCSC, RefSeq primary) — coordinate systems may differ and require liftover
- • High-volume bulk queries — rate limits apply; use Ensembl BioMart or FTP downloads for bulk data
Interface
Authentication
No authentication required. Completely open public API. Rate limits enforced by IP address.
Pricing
Free public API funded by EMBL-EBI and the Wellcome Sanger Institute. No paid tiers. Commercial use permitted.
Agent Metadata
Known Gotchas
- ⚠ Ensembl IDs are version-specific (ENSG00000123456.5) — use unversioned IDs to get current annotation
- ⚠ Genome assembly version matters — GRCh38 vs GRCh37 endpoints are separate (grch37.rest.ensembl.org)
- ⚠ POST endpoints available for batch lookups — agents should batch requests to respect rate limits
- ⚠ Cross-species ortholog queries can return large payloads for highly conserved genes
- ⚠ Ensembl release schedule is biannual — IDs and annotations can change between releases
Alternatives
Full Evaluation Report
Detailed scoring breakdown, competitive positioning, security analysis, and improvement recommendations for Ensembl REST API.
Scores are editorial opinions as of 2026-03-06.