generated: '2026-09-06'
method: probed
source: >-
  https://clinicaltrials.gov/data-api/about-api and https://clinicaltrials.gov/data-api/api
  (searched, no limits documented) plus live response-header inspection of
  https://clinicaltrials.gov/api/v2/studies on 2026-09-06
limit_count: 0
note: >-
  ClinicalTrials.gov publishes NO rate limits for the Data API v2. The developer pages state
  no request ceiling, no burst allowance and no throttling policy, and the live API returns
  no rate-limit headers at all. An agent therefore has no runtime signal telling it when it
  is close to being throttled and no documented status code to expect on exhaustion — it can
  only discover a limit by hitting one. Recorded as an honest zero.
limits: []
response_headers:
  observed: []
  checked:
  - X-RateLimit-Limit
  - X-RateLimit-Remaining
  - X-RateLimit-Reset
  - RateLimit
  - RateLimit-Policy
  - Retry-After
  evidence: >-
    HEAD/GET https://clinicaltrials.gov/api/v2/studies?pageSize=1 -> 200. Response headers
    returned were date, server (istio-envoy), strict-transport-security, x-frame-options,
    content-type, etag, x-envoy-upstream-service-time, set-cookie, x-ua-compatible,
    x-xss-protection, via, alt-svc. None of the checked rate-limit headers was present.
exhaustion_status_code: null
exhaustion_note: >-
  Undocumented. No 429 response is declared in any openapi/ document and none was observed.
adjacent_pace_signals:
- source: https://clinicaltrials.gov/robots.txt
  status: 200
  signal: 'Crawl-delay: 1'
  note: >-
    The only published pacing number on the domain. It is a crawler directive, and the same
    file carries "Disallow: /api/" — so it governs indexing bots, not API clients. Recorded
    because it is the nearest thing to a published throttle, NOT as an API rate limit.
- source: openapi/_original/clinical-trials-gov-openapi.yml
  signal: pageSize maximum 1000
  note: >-
    A per-response size ceiling, not a rate limit. It does bound how fast a client can drain
    the registry through GET /studies.