Clinical Trials MCP Server

Search Trials

search_trials

Find ClinicalTrials.gov studies by condition, status, phase, intervention, or location; supply at least one filter to narrow results.

Instructions

Search ClinicalTrials.gov for studies matching the given filters.

At least one filter should be supplied; an unfiltered search returns the whole registry one page at a time. Ordering is whatever the API returns for the query; this tool does not re-sort.

Input Schema

TableJSON Schema

Name	Required	Description
`phases`	No	Phase filter, e.g. ['Phase 2', 'Phase 3']. Omit for all phases.
`location`	No	City, state, or country text matched against study sites.
`statuses`	No	Status filter, e.g. ['RECRUITING']. Other values include NOT_YET_RECRUITING, ACTIVE_NOT_RECRUITING, ENROLLING_BY_INVITATION, COMPLETED, SUSPENDED, TERMINATED, WITHDRAWN.
`condition`	No	Condition or disease, e.g. 'type 2 diabetes'.
`page_size`	No	Results per page, 1 to 50.
`page_token`	No	Token from a previous result's next_page_token, for paging.
`intervention`	No	Drug, device, or procedure name, e.g. 'metformin'.

Output Schema

TableJSON Schema

Name	Required	Description
`trials`	No
`page_size`	Yes
`total_count`	No	Total studies matching the query, when the API reports it.
`returned_count`	Yes
`next_page_token`	No	Pass back as page_token to fetch the next page; null on the last page.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Oct 15, 2026

TDQS

A4/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the burden and does disclose meaningful behavior: results come back one page at a time, ordering follows the API and is not re-sorted, and unfiltered queries are expensive. It omits result shape (mitigated by the output schema) and any auth/rate-limit notes.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences, front-loaded with what it does, then the filter requirement, then the ordering caveat. Nothing is redundant or padded.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 7-parameter read tool with an output schema, the description covers the essentials: filter requirement, pagination via pages, and ordering. It stops short of pointing at siblings for single-trial or site lookups, a minor gap given the schema handles return values.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so every filter, including enum-like statuses and page_size bounds, is already documented. The description adds no syntax or format detail beyond the schema, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Search ClinicalTrials.gov for studies') plus the mechanism (matching given filters). It is clearly distinct from get_trial, but the description never names or contrasts those siblings explicitly, so it lands at clear-but-undifferentiated.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives a concrete usage rule: supply at least one filter, because an unfiltered search returns the whole registry page by page. That is real when-to-use context, but no alternative tool (e.g. get_trial for a known ID) is named to route the agent elsewhere.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Deploy Server