ClinicalTrials.gov API

Name: ClinicalTrials.gov API API
Brand: ClinicalTrials.gov API
Availability: InStock

✓ Official Vendor SpecHealthcareClinical Datanone6 EndpointsREST

For Agents

Search clinical trials by condition, intervention, or sponsor, retrieve individual study records by NCT ID, and query trial statistics from the ClinicalTrials.gov registry without authentication.

Quickstart

Get started with ClinicalTrials.gov API in minutes using your preferred integration method.

# Add to your MCP client config (Claude Desktop, Cursor, Windsurf)
{
  "jentic": {
    "url": "https://api.jentic.com/mcp",
    "auth": "oauth"
  }
}

# Then ask your agent:
"search for clinical trials by condition"

# → Jentic returns the GET /events tool with parameter schema, agent executes.

Capabilities

What an agent can do with ClinicalTrials.gov API API.

Search clinical studies with full-text queries filtered by condition, intervention, sponsor, status, and location

Retrieve complete study records by NCT identifier including protocol, eligibility criteria, and outcome measures

Query available study field metadata to understand the data model and construct precise filters

Get aggregate statistics on study counts by status, phase, or other field values

GET STARTED

Start building with ClinicalTrials.gov API API

Explore with Jentic

View OpenAPI Spec

Use Cases

Patterns agents use ClinicalTrials.gov API API for, with concrete tasks.

★ AI Agent Clinical Trial Discovery

AI agents search ClinicalTrials.gov through Jentic to match patients with eligible studies or generate research intelligence. An agent searches by intent, loads the studies endpoint schema, and executes queries with condition and location filters. Results return structured study records with eligibility criteria, contact information, and enrollment status — enabling automated patient-trial matching workflows.

Search for recruiting Phase 3 trials for 'non-small cell lung cancer' in the United States, then retrieve eligibility criteria for the top 3 results by enrollment count

Clinical Trial Search and Filtering

Query the ClinicalTrials.gov database with full-text search combined with structured filters for study status (recruiting, completed, not yet recruiting), phase (1-4), intervention type, condition, sponsor, and geographic location. The GET /studies endpoint returns paginated results with customizable field selection, enabling precise research queries across over 500,000 registered studies.

Search for all recruiting studies with intervention type 'Drug' for condition 'Alzheimer Disease' in Phase 2 or Phase 3, limited to the first 20 results

Individual Study Record Retrieval

Fetch complete study records by NCT identifier to access protocol details, eligibility criteria, primary and secondary outcome measures, study arms, intervention descriptions, and responsible party information. The GET /studies/{nctId} endpoint returns the full structured record for compliance review, patient eligibility assessment, or research portfolio tracking.

Retrieve the full study record for NCT04280705, extract the inclusion and exclusion criteria, and list the primary outcome measures with their time frames

Research Analytics and Statistics

Generate aggregate statistics on clinical trial activity by querying study counts, field value distributions, and registration trends. The /stats/size endpoint provides total counts with filters applied, while /stats/fieldValues/{fieldName} returns value frequency distributions for any study field. Useful for market research, competitive intelligence, and regulatory landscape analysis.

Get the total count of studies with status 'Recruiting' and condition containing 'breast cancer', then retrieve the distribution of study phases for those results

Key Endpoints

6 endpoints — search, filter, and retrieve clinical study records from the clinicaltrials.

METHOD

PATH

DESCRIPTION

GET

/studies

Search and filter clinical studies

GET

/studies/{nctId}

Get a study by NCT ID

GET

/studies/metadata

Get study field metadata

GET

/stats/size

Get study count statistics

GET

/stats/fieldValues/{fieldName}

Get field value distributions

GET

/version

Get API version information

GET

/studies

Search and filter clinical studies

GET

/studies/{nctId}

Get a study by NCT ID

GET

/studies/metadata

Get study field metadata

GET

/stats/size

Get study count statistics

GET

/stats/fieldValues/{fieldName}

Get field value distributions

Why though Jentic?

Three things that make agents converge on Jentic-routed access.

Credential isolation

ClinicalTrials.gov requires no authentication, but Jentic still provides value by managing request pacing (recommended 3 req/sec limit) and caching frequent queries to reduce load on the public endpoint.

Intent-based discovery

Agents search by intent (e.g., 'find recruiting cancer trials') and Jentic returns matching ClinicalTrials.gov operations with their filter parameter schemas, so the agent can construct precise queries without reading API documentation.

Time to first call

Direct ClinicalTrials.gov integration: 1-2 days for endpoint discovery, parameter mapping, and pagination handling. Through Jentic: under 30 minutes — search, load schema, execute with built-in pagination support.

Related APIs

Alternatives and complements available in the Jentic catalogue.

Complementary

NLM Clinical Tables

NLM lookup tables for medical conditions, drugs, and coding systems used in trial data

Choose NLM Clinical Tables when you need to resolve medical terminology, ICD codes, or drug names referenced in ClinicalTrials.gov records

Complementary

1upHealth API

Patient health data aggregation for matching real patient records against trial eligibility

Choose 1upHealth when you need to pull actual patient medical data to match against eligibility criteria found in ClinicalTrials.gov

Complementary

Healthcare.gov API

Health insurance marketplace data for understanding coverage implications of trial participation

Choose Healthcare.gov when patients need to understand insurance coverage options alongside clinical trial participation

FAQs

Specific to using ClinicalTrials.gov API API through Jentic.

Does the ClinicalTrials.gov API require authentication?

No. The ClinicalTrials.gov API v2 is publicly accessible without authentication. No API key, OAuth token, or registration is required. Through Jentic, agents can discover and call these endpoints immediately without any credential setup.

Can I search for clinical trials by medical condition?

Yes. The GET /studies endpoint accepts a query.cond parameter for condition-based filtering. You can combine it with other filters like query.term for full-text search, filter.overallStatus for enrollment status, and filter.phase for trial phase. For example, query.cond=diabetes&filter.overallStatus=RECRUITING returns actively recruiting diabetes trials.

What are the rate limits for the ClinicalTrials.gov API?

ClinicalTrials.gov does not enforce strict per-key rate limits since no authentication is required. However, the API documentation recommends limiting requests to 3 per second to avoid being blocked. Excessive automated queries may result in IP-based throttling.

How do I retrieve a specific trial's eligibility criteria through Jentic?

Search Jentic for 'get clinical trial eligibility criteria' to discover the GET /studies/{nctId} endpoint. Provide the NCT identifier (e.g., NCT04280705) and the response includes eligibilityModule with inclusion/exclusion criteria, age limits, and gender restrictions. Install via pip install jentic and use the search-load-execute flow.

Can I get statistics on how many trials exist for a condition?

Yes. The GET /stats/size endpoint returns the total count of studies matching your filters. For example, adding filter.condition=breast+cancer returns the count of breast cancer trials. The GET /stats/fieldValues/{fieldName} endpoint breaks down results by any field, such as phase distribution or sponsor frequency.

What data fields are available in study records?

The GET /studies/metadata endpoint returns the complete data model with all available fields. Study records include identification (NCT ID, title, acronym), status, sponsor, conditions, interventions, outcome measures, eligibility criteria, study design, arms/groups, references, and results when available.