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Chembl MCP Server

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Chembl MCP Server is answering right now. Last checked 14 min ago. 208 installs a week from npm. It exposes 7 tools. Last commit 29 Oct 2026.

Link compounds to protein targets, rank bioactivity, and look up drug mechanisms and indications.

Installs per day peak 225 · avg 52 · -70% w/w
a month agotoday
Uptime history 87 days of history · worst day 93%
87 days agonow
100.0%
Uptime 24h
91 of 91 checks
7
Tools
read from the server
597 ms
Response time
average over 24h
208
Installs / week
npm and PyPI

What changed 32

Every tool that appeared, vanished or quietly changed what it asks for. Recorded since 25 August 2026. No other catalogue keeps this.

29 Oct a tool changed version
24 Oct 5 tool descriptions were rewritten chembl_dataframe_describe, chembl_dataframe_query, chembl_get_bioactivities and 2 more
24 Oct 5 tools changed the parameters they ask for chembl_get_assay, chembl_get_bioactivities, chembl_get_drug_info and 2 more
24 Oct a tool changed version
18 Oct 3 tools changed the parameters they ask for chembl_dataframe_describe, chembl_dataframe_query, chembl_get_bioactivities
18 Oct 2 tool descriptions were rewritten chembl_dataframe_query, chembl_get_bioactivities
18 Oct a tool changed version
11 Oct a tool changed version
27 Sep a tool changed version
19 Sep 3 tools changed the parameters they ask for chembl_dataframe_describe, chembl_dataframe_query, chembl_get_bioactivities
and 9 more, back to 25 August 2026

Nothing serious here today

Today is the operative word: we check Chembl MCP Server every 15 minutes and re-read its code on every release. Watch it and you find out the day that stops being true.

Three servers free · no card

Connect this server

Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 14 min ago.

run in your terminal
claude mcp add chembl-mcp-server --transport http https://chembl.caseyjhand.com/mcp
Settings → Connectors → Add custom connector, then paste this address
https://chembl.caseyjhand.com/mcp
~/.codex/config.toml
[mcp_servers.chembl-mcp-server]
url = "https://chembl.caseyjhand.com/mcp"
.cursor/mcp.json
{
  "mcpServers": {
    "chembl-mcp-server": {
      "url": "https://chembl.caseyjhand.com/mcp"
    }
  }
}
.vscode/mcp.json
{
  "servers": {
    "chembl-mcp-server": {
      "type": "http",
      "url": "https://chembl.caseyjhand.com/mcp"
    }
  }
}

Available tools 7

Read directly from the server with tools/list, grouped by what they act on. If a tool disappears, we record the date.

chembl
chembl_dataframe_describe
List the tables and columns staged on a canvas by chembl_get_bioactivities — inspect before calling chembl_dataframe_query to write correct SQL. Returns each table with its row count, kind (table | view), and column names + types. Unavailable when the server sets CANVAS_PROVIDER_TYPE=none.
chembl_dataframe_query
Run a read-only SQL SELECT over the bioactivity rows chembl_get_bioactivities staged on a canvas — rank, group, dedupe, and aggregate across the FULL set, not the inline preview. Reference each staged table by the name chembl_get_bioactivities returned — bioactivities for its potency_ranked view, bioactivities_null_potency for null_potency; discover the staged tables and their columns with chembl_dataframe_describe. Compute honest aggregates here (e.g. SELECT molecule_chembl_id, MEDIAN(pchembl_value) AS med FROM bioactivities WHERE standard_type = 'IC50' GROUP BY 1 ORDER BY 2 DESC). Two independent bounds apply, each reported on its own field: truncated is true when the SQL result exceeded the canvas row cap, and rendered_rows says how many of the returned rows the markdown table holds once its character budget is reached (below row_count on a wide or long result). Page past either bound with SQL LIMIT/OFFSET — append e.g. LIMIT 500 OFFSET 500 and re-call; offsets reach rows beyond the canvas row cap. Unavailable when the server sets CANVAS_PROVIDER_TYPE=none.
chembl_get_assay
Assay provenance behind a bioactivity row: description, type (binding / functional / ADMET / toxicity), the target it measures, organism, and ChEMBL's 1–9 confidence score (9 = direct assay on the protein target, lower = homologous or indirect). Supply assay_chembl_id from a chembl_get_bioactivities row. Call this to judge whether two measurements are comparable before ranking them together.
chembl_get_bioactivities
The flagship compound↔target bioactivity bridge: measurements for a molecule (target deconvolution / selectivity), a target (lead finding), or both together (how potently one compound hits one target). Supply at least one of molecule_chembl_id (from chembl_search_molecules) or target_chembl_id (from chembl_search_targets) — supplying both narrows to that compound–target pair, supplying neither is an error. A drug's measurements are often split across its salts and other alternate forms, so molecule_chembl_id reads that one form unless include_alternate_forms widens it to the whole family under its parent (a salt's ID included), every view, page, and spill reading the same family. Filter by standard_type (IC50/Ki/EC50/…), minimum potency pchembl_value_min, assay_type, organism, and variant (wild type, or one recorded mutant such as "T315I"). Each row carries its activity_comment and data_validity_comment, its assay variant, and its source document for citation. Not every measurement has a derivable pchembl_value, so potency_view picks which side of that split you get: the default "potency_ranked" returns the measurements that have one, most potent first (ChEMBL sorts the rest first otherwise, which is why they are not merged), and "null_potency" returns exactly the measurements that have none. totalCount is the honest full match count across both views either way. Mixing measurement types (IC50 vs Ki) is a scientific error — set standard_type to compare like with like. A popular target carries tens of thousands of rows: results spill to a DataCanvas table (call chembl_dataframe_describe for its columns, then chembl_dataframe_query for honest aggregates across the staged set), while an inline preview answers the immediate question. Each view stages its own table (bioactivities / bioactivities_null_potency), so running both against one canvas_id lets a UNION ALL rebuild the full set. A canvas is minted only when a view spills; pass its canvas_id back and every later non-cursor call re-stages the table of its view with its own rows, even when they fit inline or none match, so a successful call never leaves rows from an earlier query in it, and a spill that fails or is cancelled leaves the earlier table in place. The spill is bounded by a row cap (CHEMBL_MAX_SPILL_ROWS) and a time budget (CHEMBL_SPILL_DEADLINE_MS); when either stops it short of the view, truncated is true, truncated_by names the bound, and the table is a bounded slice, not the complete view. The inline rows are always capped at limit, so compare that against totalCount before treating them as the whole answer. Spilling needs the canvas, which is on unless the server sets CANVAS_PROVIDER_TYPE=none. Whenever a call stages nothing and rows remain past this page — the canvas is off, or the view fit inline with no canvas_id — nextCursor continues the view: pass it back as cursor, with the same filters and potency_view, for the next page. A cursor page is always returned inline and never staged, canvas or not.
chembl_get_drug_info
Pharmacology for a drug (molecule): mechanism(s) of action, the molecular target(s) it acts on, action type (inhibitor / agonist / …), first-approval year, and clinical indications with the max phase reached for each. Supply molecule_chembl_id (from chembl_search_molecules) — a parent or any of its salts and other alternate forms gives the same answer: ChEMBL often records a drug's mechanisms and approved indications on a salt, so both lists cover the whole family under parent_molecule_chembl_id. Each mechanism names the form it is recorded on, and each indication is listed once per MeSH/EFO pair at the highest phase any form reached, with the forms it is recorded on, each at its own phase. Distinct from the openfda server's label/adverse-event view — this is the curated mechanism-and-indication record. A mechanism's target_chembl_id chains into chembl_get_bioactivities for compounds hitting the same target. Each list carries its own retrieval state: an empty mechanisms or indications array means the molecule has none recorded only when the matching mechanisms_status / indications_status is "complete" — "failed" means the list was not retrieved (the request ran out of time or ChEMBL answered with an error, as the matching *_failure says) and the array says nothing about the molecule, and "truncated" means the page cap fetched fewer rows than ChEMBL holds, which the matching *_total_count reports.
chembl_search_molecules
Discovery entry point for compounds. Find by name / ChEMBL ID / InChIKey with the default search_type=name (supply query), or run a structure search with search_type exact | similarity | substructure (supply structure as a SMILES). At least one of query or structure is required, and structure is required for the three structure modes. Returns ChEMBL ID, preferred name, canonical SMILES, formula, MW, AlogP, Lipinski violations, QED, max clinical phase, and the family parent_chembl_id on every row; only search_type=similarity adds a Tanimoto similarity percent. Chain molecule_chembl_id into chembl_get_bioactivities or chembl_get_drug_info. A salt often ranks ahead of its parent and carries a small share of the family's measurements, so check parent_chembl_id before chaining. A capped result carries nextCursor — pass it back as cursor with the same filters to read the next page.
chembl_search_targets
Resolve a protein/gene/UniProt accession to the ChEMBL target ID that chembl_get_bioactivities needs for the target→leads workflow. Supply at least one of accession (UniProt, e.g. P00533), gene_symbol (e.g. EGFR), or query (free-text name); filter further by organism and target_type. Returns each target with its type, organism, and component UniProt accessions + gene symbols. A UniProt accession from the uniprot/protein server is the most precise input. A capped result carries nextCursor — pass it back as cursor with the same filters to read the next page.

Endpoints

URLTransportStateLatencyChecked
https://chembl.caseyjhand.com/mcp streamable-http answering 606 ms 14 min ago

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Chembl MCP Server — questions

Answers built from our own checks of this server.

What can Chembl MCP Server do?
It exposes 7 tools, read directly from the server on our last check. Among them: chembl_dataframe_describe, chembl_dataframe_query, chembl_get_assay, chembl_get_bioactivities, chembl_get_drug_info, chembl_search_molecules and 1 more. The full list with descriptions is on this page — we take it from the server itself via tools/list, not from a README. How MCP servers expose tools in the first place →
Is Chembl MCP Server working right now?
We send a real MCP handshake every 15 minutes. Over the last 24 hours 91 of 91 checks got a reply (100.0%), average response time 597 ms. The bar chart above shows every period we have measured.
How do I connect Chembl MCP Server?
Copy the ready config from this page. We generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each in the form that client actually reads. It is a remote server, so there is nothing to install — the client connects to the address.
Does Chembl MCP Server need an API key?
No. Chembl MCP Server completed a full MCP handshake with us as an anonymous client and listed its tools without asking for anything. All 7 of them are readable on this page. This is what we observed, not what the docs claim.
How fast is Chembl MCP Server?
It answers our handshake in 597 ms on average, which is faster than 18% of all working MCP servers we measure. That is on the slow side — worth knowing if the tool sits inside an interactive loop. The comparison comes from our own checks across the whole registry, every 15 minutes.
How many people use Chembl MCP Server?
The npm package @cyanheads/chembl-mcp-server was installed 208 times in the last week. Week over week that is -70%. We show installs rather than GitHub stars on purpose: a star is a bookmark, an install is someone actually running it.
Is Chembl MCP Server open source?
The code is open source: it is published under the Apache-2.0 licence, written in TypeScript, 2 stars on GitHub and 3 open issues. The licence covers the code in the repository, not the hosted service at chembl.caseyjhand.com, which runs on its operator's own terms.