ClinicalTrials.gov
About
Search and retrieve clinical trial data from the official ClinicalTrials.gov API.
Details
- Author
- cyanheads
- Categories
- Search, Knowledge Base, Other
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Setup
Install ClinicalTrials.gov in your MCP client (Claude Desktop, Cursor, Windsurf, and others).
Repository: https://github.com/cyanheads/clinicaltrialsgov-mcp-server
Follow the installation instructions in the repository README, then restart your MCP client.
Search ClinicalTrials.gov trials, retrieve study details and results, and match patients to eligible trials via MCP. STDIO or Streamable HTTP.
Public Hosted Server:https://clinicaltrials.caseyjhand.com/mcp
Seven tools for searching, discovering, analyzing, and matching clinical trials:
Primary search tool with full ClinicalTrials.gov query capabilities.
- Full-text and field-specific queries (condition, intervention, sponsor, location, title, outcome)
- Status and phase filters with typed enum values
- Geographic proximity filtering by coordinates and distance
- Advanced AREA[] Essie expression support for complex queries
- Compact index results by default; passfieldsfor a full-fidelity projection of specific leaves (a full single record is ~70KB — fetch one withget_study_record)
- Pagination with cursor tokens, sorting by any field
Fetch posted results data for completed studies.
- Outcome measures with statistics, adverse events, participant flow, baseline characteristics
- Section-level filtering (request only the data you need)
- Optional summary mode condenses full results (~200KB) to essential metadata (~5KB per study)
- Batch multiple NCT IDs per call with partial-success reporting
- Separate tracking of studies without results and fetch errors
Match a patient profile to eligible recruiting trials.
- Takes age, sex, conditions, and location as patient demographics
- Builds optimized API queries with demographic filters (age range, sex, healthy volunteers)
- Re-ranks results so studies whose own condition matches a requested condition surface above tangential matches from the upstream fuzzy condition search
- Returns studies with eligibility and location fields for the caller to evaluate
- Bounds each candidate to the sites matching the requested location (capped bylocationLimit) rather than every site the study registers worldwide, adds the nearest recruiting site when none of the matched ones is open, and discloses what was omitted
- Provides actionable hints when no studies match (broaden conditions, adjust filters)
- Declarative tool/resource/prompt definitions with Zod schemas and format functions
- Unified error handling — handlers throw, framework catches and classifies
- Dual transport: stdio and Streamable HTTP from the same codebase
- Pluggable auth (none,jwt,oauth) for HTTP transport
- Structured logging with optional OpenTelemetry tracing
- Type-safe client for theClinicalTrials.gov REST API v2
- Public API — no authentication or API keys required
- Retry with exponential backoff (3 attempts) and rate limiting (~1 req/sec)
- HTML error detection and structured error factories
A public instance is available athttps://clinicaltrials.caseyjhand.com/mcp— no installation required. Point any MCP client at it via Streamable HTTP:
{ "mcpServers": { "clinicaltrialsgov-mcp-server": { "type": "streamable-http", "url": "https://clinicaltrials.caseyjhand.com/mcp" } } }
Add to your MCP client config (e.g.,claude_desktop_config.json):
{ "mcpServers": { "clinicaltrialsgov-mcp-server": { "type": "stdio", "command": "bunx", "args": ["clinicaltrialsgov-mcp-server@latest"], "env": { "MCP_TRANSPORT_TYPE": "stdio" } } } }
MCP_TRANSPORT_TYPE=http MCP_HTTP_PORT=3010
- Bun v1.3.0or higher (or Node.js >= 24.0.0)
git clone https://github.com/cyanheads/clinicaltrialsgov-mcp-server.git
All configuration is optional — the server works with defaults and no API keys.
bun run build bun run start:http # or start:stdio
bun run devcheck # Lints, formats, type-checks bun run test # Runs test suite
docker build -t clinicaltrialsgov-mcp-server . docker run -p 3010:3010 clinicaltrialsgov-mcp-server
SeeCLAUDE.mdfor development guidelines and architectural rules. The short version:
- Handlers throw, framework catches — notry/catchin tool logic
- Usectx.logfor request-scoped logging, noconsolecalls
- Register new tools and resources in theindex.tsbarrel files
Issues and pull requests are welcome. Run checks before submitting:
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