ClinicalTrials.gov

ClinicalTrials.gov is the U.S. National Institutes of Health (NIH) registry and results database of publicly and privately supported clinical studies of human participants conducted around the world. Operated by the National Library of Medicine (NLM), it provides a modern REST API (data-api v2) that returns study records, study metadata, search areas, and field definitions in JSON. The predecessor classic API remains available for legacy consumers but is being phased out in favor of the v2 API. Data is in the public domain and freely accessible without authentication.

ClinicalTrials.gov publishes 6 API contracts indexed on the APIs.io network, including Stats API, Studies API, Version API, and 3 more. Tagged areas include Clinical Trials, Government, Health, NIH, and Open Data.

The ClinicalTrials.gov catalog on APIs.io includes 1 JSON-LD context and 1 Spectral governance ruleset.

ClinicalTrials.gov’s developer surface includes pricing, engineering blog, documentation, developer portal, API reference, getting-started guide, support, and 26 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

34.3/100 thin ▬ flat Agent 26/100 agent aware saas Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

AccessFreeOpen⚡ Free to try

1 published contract 1 MCP Servers 2 Agent Skills

Clinical Trials Government Health NIH Open Data Public Health Research

What this lets a business do 1

Business capabilities this provider's published APIs can perform, derived from its own contracts. Browse all capabilities →

Clinical Trials Management

BC-1520

Studies

GET /studies GET /studies/{nctId}

Kin Score

Kin Score How this is scored →
scored 2026-11-06 · rubric v0.27.0

Composite quality — 34.3/100 · thin

Contract Quality 8.9 / 21

Developer Ergonomics 5.2 / 17

Access Clarity 5.4 / 17

Operational Transparency 0.0 / 11

Contract Governance 3.2 / 10

Discoverability 5.5 / 9

Regulatory Posture 3.1 / 15

Agent readiness — 26/100 · agent aware

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 6 / 6

MCP Server 0 / 12

Machine-Readable Auth 10 / 10

Idempotency 9 / 9

Stable Error Semantics 8 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 7 / 7

Typed Event Surface 0 / 6

Agent Skills 5 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 4 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 0 / 5

Distinct Operations 3 / 3

MCP Tool Quality 6 / 6

Regulatory Posture applies to this provider. Its tags matched the Government & Public Sector regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics does not apply to this provider. The published contracts declare no write operations, and a read-only API cannot create-or-update. The facet is excluded from this provider's denominator entirely — not scored zero. A reference or data API is not deficient for being unable to upsert.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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Agent readiness — checks not met, largest first (exact, from this profile):

MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0
Request/Response Examples +7 pts — share of operations carrying request/response examples; else an Examples / Code Samples link
Registration Without a Human +6 pts — a `registration_endpoint` in the served RFC 8414 / OIDC discovery document
Delegated User Identity +6 pts — a served discovery document listing authorization_code in grant_types_supported (served), else an oauth2 authorizationCode flow or openIdConnect declared in an OpenAPI (documented)
Typed Event Surface +6 pts — AsyncAPI document, OR webhooks/callbacks objects in the as-published OpenAPI, OR common[].type includes Webhooks

5 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Contract Quality scores 42.0 — up to +14.5 composite points
Developer Ergonomics scores 30.4 — up to +13.9 composite points
Access Clarity scores 31.6 — up to +13.7 composite points

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from the provider profile at artifacts.apis.io/clinical-trials-gov/apis.yml: open an issue on github.com/api-evangelist/clinical-trials-gov to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Markets this provider is in provisional

The Kin Score Market layer reads a provider inside its market: its position, and how deep its integrations go. Depth is only comparable within a position. Provisional and unweighted: not part of the Kin Score or agent readiness.

Market	Position	Depth	Registered MCP server	Declares compatibility
Life Sciences (Biotech and Pharma R&D)	standard	17.2 (thin)	-	-

Registered MCP server and declares compatibility are report only — not weighted. Undeclared means we found nothing we can read, so there is no number: we never infer integrations.

Standards implemented 1

Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.

OpenAPI

measured — observed by APIs.io (published)

APIs 6

Individual APIs this provider publishes, each with its own machine-readable definition.

ClinicalTrials.gov Classic API

RETIRED. The Classic API was withdrawn in June 2024 and its endpoints now return HTTP 404 (probed 2026-09-06: /api/query/full_studies and /api/info/data_vrs both 404). It is ret...

ClinicalTrials.gov Bulk Downloads

ClinicalTrials.gov provides bulk CSV and JSON downloads of the full study registry through the data-api download endpoints. These artifacts support large-scale analytics, archiv...

AACT Database

AACT (Aggregate Analysis of ClinicalTrials.gov) is a publicly available relational database of all ClinicalTrials.gov study content maintained by the Clinical Trials Transformat...

ClinicalTrials.gov Stats API

The Stats API from ClinicalTrials.gov — 3 operation(s) for stats.

ClinicalTrials.gov Studies API

The Studies API from ClinicalTrials.gov — 5 operation(s) for studies.

ClinicalTrials.gov Version API

The Version API from ClinicalTrials.gov — 1 operation(s) for version.

Open Collections 4

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

ClinicalTrials.gov Data API v2 Stats API

OPEN COLLECTION

ClinicalTrials.gov Data API v2 Stats Studies API

OPEN COLLECTION

ClinicalTrials.gov Data API v2 Stats Version API

OPEN COLLECTION

ClinicalTrials.gov Data API v2

OPEN COLLECTION

MCP Servers 1

Model Context Protocol servers that expose these APIs to AI agents.

ClinicalTrials.gov Data API v2 (candidate MCP surface)

A CANDIDATE tool list derived from the ClinicalTrials.gov Data API v2 OpenAPI operations. The National Library of Medicine does not publish an MCP server for ClinicalTrials.gov ...

MCP SERVER

Agent Skills 2

Packaged agent skills for driving this provider's APIs from an AI assistant.

clinical-trials-gov-find-studies

AGENT SKILL

clinical-trials-gov-get-study-record

AGENT SKILL

ClinicalTrials.gov API pricing

Prices published by ClinicalTrials.gov. A free plan or tier is listed.

Plan	Price
Public access	Free

Plan details, limits and sources →

Pricing Plans 1

Published pricing tiers and plan structures.

Clinical Trials Gov Plans Pricing

1 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Clinical Trials Gov Rate Limits

0 limits

RATE LIMITS

Service Levels 1

Uptime the provider promises or reports, as SLA4OAI. Read from its own pages; APIs.io runs no monitors.

ClinicalTrials.gov

SLA

Semantic Vocabularies 1

JSON-LD contexts and semantic vocabularies used across these APIs.

Clinical Trials Gov Context

0 classes · 7 properties

JSON-LD

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

ClinicalTrials.gov API Rules

9 rules · 3 errors 5 warnings 1 info

SPECTRAL

OpenAPI Overlays 3

Overlays applied on top of this provider's contracts. Each card says who wrote it: a document the provider publishes, or one API Evangelist derived or generated.

Clinical Trials Gov Stats Api Overlay

3 actions · update · clinical-trials-gov-stats-api-openapi.yml

DERIVED

Clinical Trials Gov Studies Api Overlay

6 actions · update · clinical-trials-gov-studies-api-openapi.yml

DERIVED

Clinical Trials Gov Version Api Overlay

3 actions · update · clinical-trials-gov-version-api-openapi.yml

DERIVED

Security Posture 2

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Clinical Trials Gov Authentication

0 schemes

SECURITY

Clinical Trials Gov Domain Security

TLSv1.3 · HSTS · DNSSEC · DMARC

SECURITY

Agentic Access 1

Recommended x-agentic-access execution contracts for AI agents.

Clinical Trials Gov Agentic Access

9 operations

9 operations · 0 acting

AGENTIC

Resources

Get Started 2

Portal, sign-up, and the first successful call

Portal

Portal

GettingStarted

GettingStarted

Documentation 2

Reference material describing how the API behaves

Documentation

Documentation

APIReference

APIReference

Agent Surfaces 3

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgenticAccess

MCPServer

MCPServer

AgentSkill

AgentSkill

Design & Contract 7

Pagination, idempotency, versioning, errors, and events

JSONLD

Spectral

Conformance

ErrorCatalog

Lifecycle

Conventions

DataModel

Scroll for all 7

Build 1

SDKs, sample code, and the tooling you integrate with

Packages

Packages

Access & Security 2

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Authentication

Authentication

Operate 7

Status, limits, changes, and where to get help

Support

FAQ

ReleaseNotes

ChangeLog

ChangeLog

Deprecation

RateLimits

Scroll for all 7

Commercial 4

Pricing, plans, and the legal terms of use

Pricing

PrivacyPolicy

TermsOfService

Plans

Company 4

The organization behind the API

Blog

Website

About

Newsroom

Other 1

Properties that don't map to a standard resource type

X-Glossary

X-Glossary

Source (apis.yml)

aid: clinical-trials-gov
name: ClinicalTrials.gov
description: ClinicalTrials.gov is the U.S. National Institutes of Health (NIH) registry and results database of publicly
  and privately supported clinical studies of human participants conducted around the world. Operated by the National Library
  of Medicine (NLM), it provides a modern REST API (data-api v2) that returns study records, study metadata, search areas,
  and field definitions in JSON. The predecessor classic API remains available for legacy consumers but is being phased out
  in favor of the v2 API. Data is in the public domain and freely accessible without authentication.
type: Index
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: true
  label: Hosted service · you call their endpoint
  confidence: high
  source:
  - openapi
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: free
  onboarding: open
  trial: false
  try_now: true
  public: true
  gated: none
  gated_source:
  - onboarding
  label: Free · Open access
  confidence: high
  source:
  - plans
  - authentication
  - rate-limits
  - security
  generated: '2026-11-06'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/clinical-trials-gov.png
url: https://raw.githubusercontent.com/api-evangelist/clinical-trials-gov/refs/heads/main/apis.yml
created: '2024-01-01'
modified: '2026-10-06'
specificationVersion: '0.23'
kind: government
tags:
- Clinical Trials
- Government
- Health
- NIH
- Open Data
- Public Health
- Research
apis:
- aid: clinical-trials-gov:classic-api
  name: ClinicalTrials.gov Classic API
  tags:
  - Clinical Trials
  - Legacy
  - REST
  image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
  baseURL: https://clinicaltrials.gov/api
  humanURL: https://clinicaltrials.gov/data-api/api
  properties:
  - url: https://clinicaltrials.gov/data-api/api
    type: Documentation
  - url: https://clinicaltrials.gov/data-api/about-api/api-migration
    type: Deprecation
  - url: lifecycle/clinical-trials-gov-lifecycle.yml
    type: Lifecycle
  description: 'RETIRED. The Classic API was withdrawn in June 2024 and its endpoints now return HTTP 404 (probed 2026-09-06:
    /api/query/full_studies and /api/info/data_vrs both 404). It is retained here only so consumers of the legacy surface
    can find the migration path. Originally the legacy ClinicalTrials.gov interface that preceded the Data API v2 and exposes
    full-study, brief-study, and field-values endpoints with XML, JSON, and CSV responses. It is being deprecated in favor
    of the v2 REST API and remains online for backward compatibility while consumers migrate.'
- aid: clinical-trials-gov:bulk-downloads
  name: ClinicalTrials.gov Bulk Downloads
  tags:
  - Bulk
  - Datasets
  - Open Data
  image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
  humanURL: https://clinicaltrials.gov/data-api/about-api/csv-download
  baseURL: https://clinicaltrials.gov/api/v2
  properties:
  - url: https://clinicaltrials.gov/data-api/about-api/csv-download
    type: Documentation
  description: ClinicalTrials.gov provides bulk CSV and JSON downloads of the full study registry through the data-api download
    endpoints. These artifacts support large-scale analytics, archival, and offline mirrors of the registry without making
    per-record API calls.
- aid: clinical-trials-gov:aact
  name: AACT Database
  tags:
  - Analytics
  - Database
  - PostgreSQL
  - Research
  tags_raw:
  - Analytics
  - Database
  - Postgres
  - Research
  image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
  humanURL: https://aact.ctti-clinicaltrials.org/
  properties:
  - url: https://aact.ctti-clinicaltrials.org/
    type: Documentation
  - url: https://aact.ctti-clinicaltrials.org/data_dictionary
    type: DataModel
  description: AACT (Aggregate Analysis of ClinicalTrials.gov) is a publicly available relational database of all ClinicalTrials.gov
    study content maintained by the Clinical Trials Transformation Initiative (CTTI) at Duke University. It is updated daily
    and is widely used by researchers as a SQL-friendly mirror of the registry.
- aid: clinical-trials-gov:clinical-trials-gov-stats-api
  name: ClinicalTrials.gov Stats API
  description: The Stats API from ClinicalTrials.gov — 3 operation(s) for stats.
  humanURL: https://clinicaltrials.gov/data-api/api
  image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
  baseURL: https://clinicaltrials.gov/api/v2
  tags:
  - Stats
  properties:
  - type: OpenAPI
    url: openapi/clinical-trials-gov-stats-api-openapi.yml
  - type: Documentation
    url: https://clinicaltrials.gov/data-api/api
  - type: About
    url: https://clinicaltrials.gov/data-api/about-api
  - type: Overlay
    url: overlays/clinical-trials-gov-stats-api-overlay.yaml
- aid: clinical-trials-gov:clinical-trials-gov-studies-api
  name: ClinicalTrials.gov Studies API
  description: The Studies API from ClinicalTrials.gov — 5 operation(s) for studies.
  humanURL: https://clinicaltrials.gov/data-api/api
  image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
  baseURL: https://clinicaltrials.gov/api/v2
  tags:
  - Studies
  properties:
  - type: OpenAPI
    url: openapi/clinical-trials-gov-studies-api-openapi.yml
  - type: Documentation
    url: https://clinicaltrials.gov/data-api/api
  - type: About
    url: https://clinicaltrials.gov/data-api/about-api
  - type: Overlay
    url: overlays/clinical-trials-gov-studies-api-overlay.yaml
- aid: clinical-trials-gov:clinical-trials-gov-version-api
  name: ClinicalTrials.gov Version API
  description: The Version API from ClinicalTrials.gov — 1 operation(s) for version.
  humanURL: https://clinicaltrials.gov/data-api/api
  image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
  baseURL: https://clinicaltrials.gov/api/v2
  tags:
  - Version
  properties:
  - type: OpenAPI
    url: openapi/clinical-trials-gov-version-api-openapi.yml
  - type: Documentation
    url: https://clinicaltrials.gov/data-api/api
  - type: About
    url: https://clinicaltrials.gov/data-api/about-api
  - type: Overlay
    url: overlays/clinical-trials-gov-version-api-overlay.yaml
common:
- type: Pricing
  url: https://clinicaltrials.gov/about-site/terms-conditions
- url: https://clinicaltrials.gov/blog/
  type: Blog
- type: AgenticAccess
  url: agentic-access/clinical-trials-gov-agentic-access.yml
- type: DomainSecurity
  url: security/clinical-trials-gov-domain-security.yml
- type: Website
  url: https://clinicaltrials.gov/
- type: About
  url: https://clinicaltrials.gov/about-site
- type: Documentation
  url: https://clinicaltrials.gov/data-api/api
- type: Portal
  url: https://clinicaltrials.gov/data-api
- type: X-Glossary
  url: https://clinicaltrials.gov/study-basics/glossary
- type: PrivacyPolicy
  url: https://www.nlm.nih.gov/privacy.html
- type: TermsOfService
  url: https://clinicaltrials.gov/about-site/terms-conditions
- type: JSONLD
  url: json-ld/clinical-trials-gov-context.jsonld
- type: Spectral
  url: rules/clinical-trials-gov-rules.yml
- type: APIReference
  url: https://clinicaltrials.gov/data-api/api
- type: GettingStarted
  url: https://clinicaltrials.gov/data-api/about-api
- type: Support
  url: https://support.nlm.nih.gov/
- type: FAQ
  url: https://clinicaltrials.gov/policy/faq
- type: Newsroom
  url: https://clinicaltrials.gov/about-site/news-and-updates
- type: ReleaseNotes
  url: https://clinicaltrials.gov/about-site/release-notes
- type: ChangeLog
  url: https://clinicaltrials.gov/about-site/release-notes
- type: ChangeLog
  url: changelog/clinical-trials-gov-changelog.yml
- type: Deprecation
  url: https://clinicaltrials.gov/data-api/about-api/api-migration
- type: Packages
  url: packages/clinical-trials-gov-packages.yml
- type: MCPServer
  url: mcp/clinical-trials-gov-mcp.yml
- type: Conformance
  url: conformance/clinical-trials-gov-conformance.yml
- type: ErrorCatalog
  url: errors/clinical-trials-gov-problem-types.yml
- type: Lifecycle
  url: lifecycle/clinical-trials-gov-lifecycle.yml
- type: Authentication
  url: authentication/clinical-trials-gov-authentication.yml
- type: Conventions
  url: conventions/clinical-trials-gov-conventions.yml
- type: DataModel
  url: data-model/clinical-trials-gov-data-model.yml
- type: Plans
  url: plans/clinical-trials-gov-plans-pricing.yml
- type: RateLimits
  url: rate-limits/clinical-trials-gov-rate-limits.yml
- type: AgentSkill
  url: skills/_index.yml
maintainers:
- FN: Kin Lane
  email: kinlane@gmail.com
x-enrichment:
  date: '2026-09-06'
  status: enriched
  artifacts_added: 18
  pass: local-v3

ClinicalTrials.gov API — frequently asked questions

Does ClinicalTrials.gov have an API?

Yes. APIs.io lists 6 APIs from ClinicalTrials.gov, including ClinicalTrials.gov Classic API, ClinicalTrials.gov Bulk Downloads and AACT Database, and 3 more.

Is there an OpenAPI specification for the ClinicalTrials.gov API?

Yes. APIs.io indexes 3 OpenAPI specifications for ClinicalTrials.gov, each linked for download from this page.

How do I authenticate with the ClinicalTrials.gov API?

ClinicalTrials.gov uses bearer-token authentication (0 schemes). The details are profiled on APIs.io as Clinical Trials Gov Authentication.

How much does the ClinicalTrials.gov API cost?

APIs.io lists 1 pricing plan for ClinicalTrials.gov, with each plan's price, limits and inclusions under Pricing on this page.

Does ClinicalTrials.gov have an MCP server?

Yes. APIs.io lists 1 MCP server for ClinicalTrials.gov: A CANDIDATE tool list derived from the ClinicalTrials.gov Data API v2 OpenAPI operations. The National Library of Medicine does not publish an MCP server for ClinicalTrials.gov — no hosted endpoint, n

Is the ClinicalTrials.gov API ready for AI agents?

ClinicalTrials.gov has a Kin Score of 34.3 out of 100 (thin) and an Agent Readiness score of 25.6 (agent-aware), scored by API Evangelist on 2026-11-06.

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Tools for providers

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find_providersBrowse and filter every provider in the catalog.
get_provider_artifactsEvery artifact this provider publishes, grouped by type.
get_provider_operationsEvery operation across all of their OpenAPIs — one call instead of parsing every spec.
get_provider_toolsEvery MCP tool they ship, with the operation each wraps.
get_provider_evidenceHow each part of their score was established. Free — the basis for a claim should not sit behind it.
get_provider_ratingPRO — composite, band, trend and facet scores.
apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
resolveTurn a domain, URL or GitHub org into the provider it belongs to.
find_cohortsEvery scored population of providers in the catalog.

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