ChEMBL API
Provides access to the EMBL-EBI ChEMBL database of 20M+ bioactive compounds with drug-likeness properties, bioactivity data against protein targets, and approved drug information for drug discovery research.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
HTTPS enforced. No auth required — appropriate for public research data. CC BY-SA licensed data. Python client has some dependencies that are not actively monitored for CVEs.
⚡ Reliability
Best When
An agent is performing drug discovery research that requires bioactivity data, compound filtering, or approved drug lookups against biological targets.
Avoid When
You need clinical trial results, patient data, or computational chemistry predictions beyond stored experimental data.
Use Cases
- • Retrieving bioactivity data (IC50, Ki, EC50) for compounds against drug targets
- • Filtering compounds by drug-likeness properties (Lipinski, TPSA, etc.)
- • Looking up approved drugs and their mechanism of action
- • QSAR modeling data preparation and structure-activity relationship analysis
- • Target-based drug discovery: finding compounds active against a protein
Not For
- • Real-time compound synthesis or reaction prediction
- • Proprietary or unpublished bioactivity data
- • Clinical outcomes data or patient-level efficacy
Interface
Authentication
No authentication required. Fully open public API operated by EMBL-EBI. No API key needed. Throttling is applied at the server level without explicit documentation of limits.
Pricing
Free public API funded by EMBL-EBI. No commercial tiers. Data is released under CC BY-SA 3.0 license.
Agent Metadata
Known Gotchas
- ⚠ Django REST Framework filter syntax (chembl_id__icontains, molecule_properties__mw_freebase__lte) is verbose and non-obvious for agents
- ⚠ Rate limits not documented; aggressive parallelism will trigger 429s without guidance on back-off
- ⚠ The Python client (chembl_webresource_client) caches aggressively — agents may get stale data in long-running sessions
- ⚠ Field names differ between the REST API and the Python client in some cases
- ⚠ Compound identifiers (ChEMBL ID, InChI, SMILES) require careful handling — not all operations accept all ID types
Alternatives
Full Evaluation Report
Detailed scoring breakdown, competitive positioning, security analysis, and improvement recommendations for ChEMBL API.
Scores are editorial opinions as of 2026-03-06.