Clinicaltrials

Ct Search

ct_search

Read-onlyIdempotent

Search ClinicalTrials.gov for clinical trials — find trials and look up a NAMED trial by keyword, condition, drug/therapy, status (e.g. 'Recruiting'), or phase (e.g. 'Phase 2'). Use for "clinical trials for <disease/drug>", or to locate a specific study like "the FLOW trial", "semaglutide kidney outcomes trial" (use ct_get_study for its full design/results). Returns NCT IDs, titles, status, enrollment, and sponsor info.

Input Schema

TableJSON Schema

Name	Required	Description
`limit`	No	Number of results (1-100, default 10)
`phase`	No	Filter by phase: EARLY_PHASE1, PHASE1, PHASE2, PHASE3, PHASE4 (or NA). Roman numerals ("Phase III") and comma-separated unions ("PHASE2,PHASE3") are accepted.
`query`	Yes	The SUBJECT of the search — a condition, drug, or keyword (e.g., "GLP-1 receptor agonist", "breast cancer immunotherapy"). Prefer the topic alone over a full sentence: put status in `status` and phase in `phase` rather than in the text. Conversational framing is stripped automatically, and the term actually searched is echoed back as `query_used`.
`status`	No	Filter by overall status: RECRUITING, ACTIVE_NOT_RECRUITING, COMPLETED, TERMINATED, WITHDRAWN, ENROLLING_BY_INVITATION, SUSPENDED, NOT_YET_RECRUITING. Several may be combined as a comma-separated union, e.g. "RECRUITING,NOT_YET_RECRUITING".
`sponsor`	No	Filter by the trial's registered LEAD sponsor (e.g., "Pfizer", "Novo Nordisk"). Widen to trials the company only partners on with sponsor_match: "lead_or_collaborator".
`sponsor_match`	No	Which sponsor role the name must fill. "lead" (the default) returns only trials whose registered LEAD sponsor is that company. "lead_or_collaborator" also returns trials led by someone else that list the company as a collaborator — typically academic trials of the company's drug. Every returned study carries sponsor_match_field naming which one matched.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`studies`	Yes	List of formatted trial summaries
`total_count`	Yes	Total number of matching trials

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedAug 29, 2026

changedInput schema / properties / sponsor / description

Previous value: -"Filter by sponsor name (e.g., \"Pfizer\", \"Novo Nordisk\")"New value: +"Filter by the trial's registered LEAD sponsor (e.g., \"Pfizer\", \"Novo Nordisk\"). Widen to trials the company only partners on with sponsor_match: \"lead_or_collaborator\"."

addedInput schema / properties / sponsor_match

Added value: +{
+  "description": "Which sponsor role the name must fill. \"lead\" (the default) returns only trials whose registered LEAD sponsor is that company. \"lead_or_collaborator\" also returns trials led by someone else that list the company as a collaborator — typically academic trials of the company's drug. Every returned study carries sponsor_match_field naming which one matched.",
+  "enum": [
+    "lead",
+    "lead_or_collaborator"
+  ],
+  "type": "string"
+}

Changed3 schema fields changedJul 30, 2026

changedInput schema / properties / phase / description

Previous value: -"Filter by phase: EARLY_PHASE1, PHASE1, PHASE2, PHASE3, PHASE4"New value: +"Filter by phase: EARLY_PHASE1, PHASE1, PHASE2, PHASE3, PHASE4 (or NA). Roman numerals (\"Phase III\") and comma-separated unions (\"PHASE2,PHASE3\") are accepted."

changedInput schema / properties / query / description

Previous value: -"Search term (e.g., \"GLP-1 receptor agonist\", \"breast cancer immunotherapy\")"New value: +"The SUBJECT of the search — a condition, drug, or keyword (e.g., \"GLP-1 receptor agonist\", \"breast cancer immunotherapy\"). Prefer the topic alone over a full sentence: put status in `status` and phase in `phase` rather than in the text. Conversational framing is stripped automatically, and the term actually searched is echoed back as `query_used`."

changedInput schema / properties / status / description

Previous value: -"Filter by overall status: RECRUITING, ACTIVE_NOT_RECRUITING, COMPLETED, TERMINATED, WITHDRAWN, ENROLLING_BY_INVITATION, SUSPENDED, NOT_YET_RECRUITING"New value: +"Filter by overall status: RECRUITING, ACTIVE_NOT_RECRUITING, COMPLETED, TERMINATED, WITHDRAWN, ENROLLING_BY_INVITATION, SUSPENDED, NOT_YET_RECRUITING. Several may be combined as a comma-separated union, e.g. \"RECRUITING,NOT_YET_RECRUITING\"."

Changed1 schema field changedMay 8, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "studies": {
+      "description": "List of formatted trial summaries",
+      "items": {
+        "properties": {
+          "collaborators": {
+            "description": "List of collaborator names",
+            "items": {
+              "type": "string"
+            },
+            "type": "array"
+          },
+          "completion_date": {
+            "description": "Final completion date",
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "conditions": {
+            "description": "List of trial conditions",
+            "items": {
+              "type": "string"
+            },
+            "type": "array"
+          },
+          "enrollment": {
+            "description": "Target enrollment count",
+            "type": [
+              "number",
+              "null"
+            ]
+          },
+          "enrollment_type": {
+            "description": "Enrollment type (e.g., Actual, Anticipated)",
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "interventions": {
+            "description": "List of interventions",
+            "items": {
+              "properties": {
+                "description": {
+                  "description": "Intervention description",
+                  "type": [
+                    "string",
+                    "null"
+                  ]
+                },
+                "name": {
+                  "description": "Intervention name",
+                  "type": [
+                    "string",
+                    "null"
+                  ]
+                },
+                "type": {
+                  "description": "Intervention type",
+                  "type": [
+                    "string",
+                    "null"
+                  ]
+                }
+              },
+              "type": "object"
+            },
+            "type": "array"
+          },
+          "nct_id": {
+            "description": "NCT identifier",
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "official_title": {
+            "description": "Official trial title",
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "phase": {
+            "description": "Trial phase(s) comma-separated",
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "primary_completion_date": {
+            "description": "Primary completion date",
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "sponsor": {
+            "description": "Lead sponsor name",
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "sponsor_class": {
+            "description": "Sponsor class",
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "start_date": {
+            "description": "Trial start date",
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "status": {
+            "description": "Overall trial status",
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "title": {
+            "description": "Brief trial title",
+            "type": [
+              "string",
+              "null"
+            ]
+          }
+        },
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "total_count": {
+      "description": "Total number of matching trials",
+      "type": "number"
+    }
+  },
+  "required": [
+    "total_count",
+    "studies"
+  ],
+  "type": "object"
+}

Changed1 schema field changedMay 6, 2026

addedInput schema / examples

Added value: +[
+  {
+    "limit": 20,
+    "phase": "PHASE2",
+    "query": "GLP-1 receptor agonist",
+    "status": "RECRUITING"
+  },
+  {
+    "limit": 10,
+    "query": "breast cancer immunotherapy",
+    "sponsor": "Pfizer"
+  }
+]

First observedApr 22, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already declare read-only, idempotent, non-destructive behavior. The description adds the return field set (NCT IDs, titles, status, enrollment, sponsor) and the query normalization behavior (conversational framing stripped, echoed as query_used), which sets useful expectations. No contradiction.

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?

Two dense sentences with front-loaded purpose, concrete usage examples, an explicit alternative, and a concise return summary. Every sentence earns its place with no filler.

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

Completeness5/5

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

For a read-only search tool with a rich output schema, fully documented parameters, and annotations covering safety, the description leaves no critical gaps. It also covers query normalization and sponsor matching behavior, making the tool easy to invoke correctly.

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 coverage is 100% with rich descriptions for every parameter, including enums, union syntax, default limit, and sponsor_match semantics. The main description adds example phrasings but does not meaningfully go beyond what the schema already provides, so the baseline of 3 is appropriate.

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

Purpose5/5

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

The description opens with a specific verb and resource ('Search ClinicalTrials.gov for clinical trials') and immediately scopes the search dimensions (keyword, condition, drug/therapy, status, phase). It also distinguishes itself from ct_get_study, so an agent can select it correctly without opening the schema.

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

Usage Guidelines5/5

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

Explicitly says 'Use for' with concrete query examples like 'clinical trials for <disease/drug>' and named-trial lookup, and directs full design/results queries to ct_get_study. This gives the agent clear when-to-use guidance and names an alternative.

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

All Clinicaltrials tools Inspect

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