PubMed MCP Server

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Overview

Biomedical literature from PubMed, PubMed Central, and Europe PMC. Search it, fetch metadata and full text, resolve identifiers and partial citations, format references, and ground queries in MeSH vocabulary. Runs as a stdio process, a local Streamable HTTP server, or the public hosted endpoint above.

Tools

Tool	Description
pubmed_search_articles	Search PubMed with full query syntax, structured filters, date ranges, and optional summaries
pubmed_fetch_articles	Fetch article metadata by PMID: abstract, authors, journal, MeSH terms, databank accessions such as trial registration IDs, grants, a collective author's investigators on request, linked retraction and correction notices
pubmed_fetch_fulltext	Fetch full text by PMID, PMCID, or DOI, falling back from PMC to Europe PMC to Unpaywall
pubmed_europepmc_search	Search Europe PMC for preprints, patents, Agricola, and open-access records PubMed doesn't carry
pubmed_europepmc_fetch	Fetch complete Europe PMC records, including the untruncated abstract, as records: [{ source, epmcId }]
pubmed_fetch_citation_metrics	Fetch NIH iCite citation metrics by PMID: Relative Citation Ratio, NIH percentile, citation counts and rates
pubmed_format_citations	Format citations in APA 7th, MLA 9th, BibTeX, RIS, or Vancouver (ICMJE/NLM), with linked retraction and correction notices
pubmed_find_related	Find similar articles, citing articles, or references for a PMID
pubmed_spell_check	Correct a misspelled PubMed query via NCBI ESpell
pubmed_lookup_mesh	Look up MeSH headings with tree numbers, scope notes, and entry terms
pubmed_lookup_citation	Resolve partial references, up to 25 at a time, to PMIDs via ECitMatch
pubmed_convert_ids	Convert between DOI, PMID, and PMCID via the PMC ID Converter

Resources

Resource	Description
pubmed://database/info	PubMed database metadata via EInfo (field list, record count, last update)

Prompts

Prompt	Description
research_plan	Generate a structured four-phase biomedical research plan

Capability reference

pubmed_search_articles _tool

• Full PubMed query syntax plus filters (author, journal, MeSH, publication type, language, species, abstract, free full text) and publication/modification/Entrez date ranges
• Up to 1,000 results per page and offsets up to 9,998, or maxResults: 0 for the match count alone; summaryCount adds briefs for up to 50 hits
• Reports totalCount, the effectiveQuery PubMed ran, and the appliedFilters
• Rejects blank filter values, impossible dates, and reversed date ranges before PubMed is called

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pubmed_fetch_articles _tool

• Up to 200 PMIDs per call; misses are listed in unavailablePmids
• Abstract, authors, journal, DOI, publication types, linked retraction/erratum/comment notices, and links; MeSH terms on by default, grants via includeGrants, and the members of a collective author (its InvestigatorList, thousands on some consortium trials) via includeInvestigators
• A retracted, corrected, or questioned article opens with the same notice block as pubmed_format_citations, directly under its title
• dataBanks lists the record's trial registrations and data deposits (ClinicalTrials.gov NCT IDs, GenBank and PDB accessions, Dryad DOIs) verbatim; search pubmed_search_articles for <accession>[si] to find other records citing one
• recordType separates journal articles from Bookshelf chapters and books; opt-in maxResponseCharacters defers overflow to deferred.ids

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pubmed_fetch_fulltext _tool

• pmcids, pmids, and dois in any mix, up to 50 distinct identifiers per call: the first 10 are fetched and the rest returned in overLimit for a follow-up call. Each is tried against PMC, then Europe PMC, then Unpaywall (needs UNPAYWALL_EMAIL); an article several of them name is fetched and returned once, and viaSource names the tier that answered
• source: "pmc" returns sections (the body, then back matter such as acknowledgments, declarations, and appendices), tables, and figures; source: "unpaywall" returns a best-effort HTML or PDF text body
• Europe PMC full text is fetched for records Europe PMC marks open access, preprints included; articles carry the licenses their PMC JATS states
• Misses carry a typed reason and triedTiers; sections, maxSections, maxCharacters, overflowMode, and maxResponseCharacters bound the response, truncation reports what was cut, and sectionCap names the sections maxSections cut

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pubmed_europepmc_search _tool

• Adds preprints (PPR), patents (PAT), and Agricola (AGR) to MED and PMC; defaults to MED, PMC, PPR
• Cursor pagination via cursorMark / nextCursorMark, up to 100 per page; abstracts arrive as 400-character snippets
• Optional sort of comma-separated <field> asc|desc keys; relevance is the default order, and a sort Europe PMC cannot use fails as europepmc_invalid_input
• Hits carry license and hasFullTextXml
• Not registered when EUROPEPMC_ENABLED=false

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pubmed_europepmc_fetch _tool

• Up to 25 records per call as records: [{ source, epmcId }], each pair copied from a search hit, with the full abstract, license, and hasFullTextXml; unresolved ids land in notFound; opt-in maxResponseCharacters defers overflow to deferred.records
• Not registered when EUROPEPMC_ENABLED=false

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pubmed_fetch_citation_metrics _tool

• Up to 1,000 PMIDs per call; the first 200 distinct are fetched and the rest returned in overLimit, PMIDs NIH iCite has no record for in unavailablePmids
• Relative Citation Ratio (with a provisional flag), NIH percentile, citation count and rates, Approximate Potential to Translate, MeSH category shares, and clinical citations
• iCite does not flag retractions; check pubmed_fetch_articles for notices
• Source: NIH iCite

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pubmed_format_citations _tool

• Up to 50 PMIDs per call, in any mix of apa, mla, bibtex, ris, and vancouver
• Bookshelf records cite as edited books, each chapter dated by its own last revision or contribution date; PMIDs that can't be fetched are reported as unavailable
• Vancouver writes page ranges in elided Citing Medicine form (1637-1645 → 1637-45); BibTeX issn and RIS SN carry the journal's linking ISSN, and RIS TI drops its trailing period
• Retractions, errata, and expressions of concern NCBI links to an article come back as notices and are shown ahead of its citations; Vancouver adds a Retraction in: / Erratum in: note and APA a retraction parenthetical

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pubmed_find_related _tool

• similar, cited_by, or references, up to 50 per page with offset pagination
• Falls back to Europe PMC, then OpenAlex, and names the provider that answered; fails as all_providers_failed if none can

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pubmed_spell_check _tool

• Returns original, corrected, and hasSuggestion; corrections land in place, so field tags, operators, spacing, and gene symbols stay as written, and a single letter such as an author initial is never swapped for another
• Values of indexed field tags (aged[mh], zhang y[au], free full text[sb]) are kept as written; free-text fields ([tiab], [ti], [tw]) are still corrected
• Run it after a zero-hit or thin search, then retry pubmed_search_articles with corrected

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pubmed_lookup_mesh _tool

• Descriptors by name or free-text term, with an exact heading match pinned first (the descriptor, for a drug-class heading); up to 50 per page, continued via nextOffset
• Records carry their MeSH unique ID (meshId, e.g. D000072657) beside the Entrez UID; includeDetails (default on) adds tree numbers, scope notes, and entry terms

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pubmed_lookup_citation _tool

• Up to 25 partial citations per call; a journal or a four-digit year is required, and volume, first page, and author sharpen the match
• Each is matched independently and comes back matched, not_found, or ambiguous, with recovery detail

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pubmed_convert_ids _tool

• Up to 50 ids per call, all of one declared idType (doi, pmid, pmcid); only PMC-indexed articles resolve
• One success or error row per id, in order, so a partial batch never fails

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pubmed://database/info _resource

• Live EInfo call for the pubmed database, returned as application/json
• count, lastUpdate, and fields[], whose names are the search tags pubmed_search_articles accepts

---

research_plan _prompt

• Arguments: title, goal, and keywords required; organism and includeAgentPrompts optional
• Returns a four-phase research plan; includeAgentPrompts: "true" adds an agent-guidance block under each of its nine sub-steps, two of which point at tools: the literature review names pubmed_search_articles and pubmed_lookup_mesh, and the interpretation step names pubmed_search_articles

Features

Built on @cyanheads/mcp-ts-core: stdio and Streamable HTTP transports, pluggable auth (none / jwt / oauth), swappable storage (in-memory, filesystem, Supabase, Cloudflare KV/R2/D1), structured logging with optional OpenTelemetry tracing.

PubMed-specific:

• NCBI E-utilities (ESearch, EFetch, ESummary, ELink, ESpell, EInfo, ECitMatch) and the PMC ID Converter, with Europe PMC, OpenAlex, and Unpaywall filling the gaps
• Shared NCBI request queue: paced request starts, capped concurrency, a cooldown that holds every caller after an NCBI 429, and one deadline covering queue wait and retries
• XML parsing built for PubMed's inconsistent records: structured abstracts, missing fields, varying date formats
• Forgiving identifiers: a zero-padded PMID resolves as the PMID it spells in every tool that takes one; pubmed_fetch_fulltext also matches DOIs case-insensitively and PMC IDs with or without the PMC prefix
• Hand-rolled citation formatters (APA, MLA, BibTeX, RIS, Vancouver) with no dependencies

Agent-friendly output:

• Provenance in responses: source labels, license fields on full-text and Europe PMC results, best-effort warnings on Unpaywall results, and effective-query echo on searches, so agents can judge what to trust
• Graceful partial failure: batch tools return per-item success/error rows instead of failing the request, with structured status codes and actionable next-step text
• Discriminated output contracts: source: "pmc" | "unpaywall", typed unavailable reasons, viaSource and triedTiers fields, so callers branch on data, not string parsing

Getting started

Connect to the hosted instance, no install:

claude mcp add --transport http pubmed-mcp-server https://pubmed.caseyjhand.com/mcp

Or run it locally:

claude mcp add pubmed-mcp-server -- npx -y @cyanheads/pubmed-mcp-server

For other clients, add this to the MCP config file:

{
  "mcpServers": {
    "pubmed-mcp-server": {
      "command": "npx",
      "args": ["-y", "@cyanheads/pubmed-mcp-server"]
    }
  }
}

An NCBI API key in NCBI_API_KEY raises the rate limit from 3 to 10 requests per second (-e NCBI_API_KEY=your-key, or an env entry). For Docker or a source build, see Running the server.

Configuration

Variable	Description	Default
NCBI_API_KEY	NCBI API key; raises the rate limit from 3 to 10 req/s.	none
NCBI_ADMIN_EMAIL	Contact email sent with NCBI requests, as NCBI recommends.	none
NCBI_REQUEST_DELAY_MS	Minimum gap between NCBI request starts, in ms.	400 (100 with a key)
NCBI_MAX_CONCURRENT	Max concurrent in-flight NCBI requests.	8
NCBI_MAX_RETRIES	Retry attempts for failed NCBI requests.	6
NCBI_TIMEOUT_MS	Per-request HTTP timeout, in ms.	30000
NCBI_TOTAL_DEADLINE_MS	Deadline for one NCBI call across queue wait, retries, and backoff, in ms. A call that can't start in time is rejected at once.	60000
UNPAYWALL_EMAIL	Contact email for Unpaywall. Setting it enables the Unpaywall tier of pubmed_fetch_fulltext for non-PMC DOIs.	none
UNPAYWALL_TIMEOUT_MS	Per-request timeout for Unpaywall lookups and content fetches, in ms.	20000
EUROPEPMC_ENABLED	Set false to disable every Europe PMC call: both Europe PMC tools go unregistered, pubmed_fetch_fulltext skips that tier, and pubmed_find_related skips that fallback.	true
EUROPEPMC_EMAIL	Optional contact email sent with Europe PMC requests.	none
EUROPEPMC_REQUEST_DELAY_MS	Minimum gap between Europe PMC request starts, in ms.	200
EUROPEPMC_MAX_RETRIES	Retry attempts for failed Europe PMC requests.	3
EUROPEPMC_TIMEOUT_MS	Per-request timeout for Europe PMC calls, in ms.	20000
MCP_TRANSPORT_TYPE	Transport: stdio or http.	stdio
MCP_HTTP_PORT	HTTP server port.	3010
MCP_SESSION_MODE	HTTP session mode: stateless, stateful, or auto.	stateless
MCP_AUTH_MODE	Authentication: none, jwt, or oauth.	none
MCP_LOG_LEVEL	Log level (debug, info, warning, error, etc.).	info
LOGS_DIR	Directory for log files (Node.js only).	<app-root>/logs
STORAGE_PROVIDER_TYPE	Storage backend: in-memory, filesystem, supabase, cloudflare-kv/r2/d1.	in-memory
OTEL_ENABLED	Enable OpenTelemetry.	false

See .env.example for every server setting and the common framework overrides.

Running the server

Local development

Requires Bun v1.4.0 or higher (or Node.js v24+).

• Clone and install:

  git clone https://github.com/cyanheads/pubmed-mcp-server.git
  cd pubmed-mcp-server && bun install
  cp .env.example .env   # set NCBI_API_KEY, NCBI_ADMIN_EMAIL, and UNPAYWALL_EMAIL as needed
  

• Build and run the production version:

  # One-time build
  bun run rebuild
  
  # Run the built server
  bun run start:http
  # or
  bun run start:stdio
  

• Run checks and tests:

  bun run devcheck  # Lints, formats, type-checks, and more
  bun run test      # Runs the test suite
  

Docker

docker run --rm -p 3010:3010 ghcr.io/cyanheads/pubmed-mcp-server:latest

The image defaults to HTTP transport, stateless session mode, and logs to /var/log/pubmed-mcp-server. To run it over stdio from an MCP client, use "command": "docker" with "args": ["run", "-i", "--rm", "-e", "MCP_TRANSPORT_TYPE=stdio", "ghcr.io/cyanheads/pubmed-mcp-server:latest"]. To build locally, docker build -t pubmed-mcp-server .; OpenTelemetry peer dependencies are installed by default — build with --build-arg OTEL_ENABLED=false to omit them.

Project structure

Directory	Purpose
src/mcp-server/tools	Tool definitions (*.tool.ts). Twelve tools across PubMed, PMC, Europe PMC, and NIH iCite.
src/mcp-server/resources	Resource definitions. Database info resource.
src/mcp-server/prompts	Prompt definitions. Research plan prompt.
src/services/ncbi	NCBI E-utilities service layer — API client, queue, parser, formatter.
src/services/europe-pmc	Europe PMC service — search + fullTextXML JATS retrieval. Reuses the NCBI JATS parser.
src/services/unpaywall	Unpaywall service — DOI → OA location resolution and content fetch (HTML/PDF).
src/services/openalex	OpenAlex service — last-resort provider for pubmed_find_related.
src/config	Server-specific environment variable parsing and validation with Zod.
tests/	Unit and integration tests, mirroring the src/ structure.

Development guide

See CLAUDE.md for development guidelines and architectural rules. The short version:

• Handlers throw, framework catches — no try/catch in tool logic
• Use ctx.log for logging, ctx.state for storage
• Register new tools and resources in the createApp() arrays in src/index.ts
• Wrap external API calls: validate raw → normalize to domain type → return output schema; never fabricate missing fields

Contributing

Issues are welcome. Run checks and tests before submitting:

bun run devcheck
bun run test

License

This project is licensed under the Apache 2.0 License. See the LICENSE file for details.