ClinicalTrials.gov API

Name: ClinicalTrials.gov 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.

Install Jentic One Beta

Connect the ClinicalTrials.gov API to your agent

Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the ClinicalTrials.gov API, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.

Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.

Step 1: Jentic One Host machine

# On the machine that will host your Jentic One instance:
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh

Step 2: Agent machine

# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh
jentic register       # connects your agent to your Jentic One instance

Jentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.

Capabilities

What an agent can do with ClinicalTrials.gov 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 STARTED

Start building with ClinicalTrials.gov API

Explore with Jentic

View OpenAPI Document

Use Cases

Patterns agents use ClinicalTrials.gov 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 Jentic?

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

Credential isolation

The ClinicalTrials.gov API needs no credential, so there is nothing to store, and Jentic routes the call through the same execution flow as authenticated tools. No secret enters the agent's prompt, logs, or context.

Intent-based discovery

Agents search Jentic by intent such as 'find recruiting cancer trials' or 'get a study by NCT id', and Jentic returns the matching ClinicalTrials.gov operation with its filter parameter schema, so the agent constructs precise queries without browsing the reference docs.

Time to first call

FAQs

Specific to using ClinicalTrials.gov 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.

Can I limit what my agent is allowed to do with the ClinicalTrials.gov API?

Yes. Because you run Jentic One yourself, your own rules decide which ClinicalTrials.gov operations your agent may call. The API is read-only and needs no credentials, so you can allow only the operations you need, such as searching studies with GET /studies or fetching study metadata with GET /studies/metadata, while withholding others like the /stats endpoints. That set stays limited to exactly the read operations you permit.