ClinicalTrials.gov API
✓ 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.
Use for: Search for clinical trials treating Type 2 diabetes, I need to find active trials for a specific drug, Retrieve the full protocol for trial NCT04280705, List all Phase 3 trials sponsored by a specific company
Not supported: Does not handle patient health records, trial enrollment submissions, or regulatory filings — use for clinical trial search, metadata retrieval, and statistical queries only.
Search, filter, and retrieve clinical study records from the ClinicalTrials.gov database — the world's largest registry of clinical trials with over 500,000 studies across 220 countries. The v2 API provides 6 endpoints for full-text study search with field-level filtering, individual study retrieval by NCT ID, metadata inspection, and statistical queries. No authentication is required for public access.
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.
1
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 | sh2
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 instanceJentic 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 aggregate statistics on study counts by status, phase, or other field values
Access field-level value distributions for analytical and reporting purposes
Monitor API version and availability for integration health checks
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
GET
/version
Get API version information
Why 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.
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.
GET STARTED