generated: '2026-09-05'
method: derived
provider: Cancer.gov
providerId: cancer-gov
source: Derived from the eight first-party OpenAPI documents in openapi/_original/ and the live GDC GraphQL
  schema, cross-checked against https://docs.gdc.cancer.gov/API/Users_Guide/Getting_Started/, https://api.seer.cancer.gov/docs
  and https://api.seer.cancer.gov/terms.
overview: Cancer.gov is not one API with one set of conventions — it is six independently built and independently
  operated NCI programs (Clinical Trials Search, GDC, SEER, EVS, MoDaC, and the five webapis.cancer.gov
  content services) that share a domain and nothing else. Auth header, pagination parameter names, error
  envelope and versioning scheme all differ per service, and an integrator has to learn each one separately.
auth:
  style: api-key-header, and it is a different header on every service
  schemes:
  - api: cancer-gov:clinical-trials-api
    header: X-API-KEY
    required: true
    evidence: Live GET https://clinicaltrialsapi.cancer.gov/api/v2/trials without a key returns HTTP 401.
  - api: cancer-gov:seer-api
    header: X-SEERAPI-Key
    required: true
    evidence: components.securitySchemes.apiKeyScheme in https://api.seer.cancer.gov/v3/api-docs; live
      GET /rest/glossary/latest returns HTTP 401 anonymously.
  - api: cancer-gov:gdc-api
    header: X-Auth-Token
    required: false
    evidence: https://docs.gdc.cancer.gov/API/Users_Guide/Getting_Started/ — required only for controlled-access
      data and submission; open data and GraphQL introspection answer anonymously.
  - api: cancer-gov:evs-api
    header: null
    required: false
    evidence: No securityScheme in the spec; live GET https://api-evsrest.nci.nih.gov/api/v1/metadata/terminologies
      returns HTTP 200 anonymously.
  - api: cancer-gov:glossary-api
    header: null
    required: false
    evidence: No securityScheme in any of the five webapis.cancer.gov specs; the same is true for drug-dictionary,
      sitewide-search, best-bets and r4r.
  cross_link: authentication/cancer-gov-authentication.yml
idempotency:
  supported: false
  coverage: none
  scope: null
  header: null
  retention: null
  note: 'No Idempotency-Key header is declared on any of the 84 mutating operations across the eight specs
    (SEER 53, MoDaC 29, EVS 2), and none is documented anywhere. A client that retries a POST after a
    timeout has no replay protection. coverage: none.'
pagination:
  style: offset/limit, with different parameter names per service
  cursor: false
  variants:
  - api: cancer-gov:seer-api
    params:
    - page
    - per_page
    - offset
    - from
    - order
  - api: cancer-gov:evs-api
    params:
    - pageSize
    - limit
    - sort
  - api: cancer-gov:glossary-api
    params:
    - size
    - from
  - api: cancer-gov:drug-dictionary-api
    params:
    - size
    - from
  - api: cancer-gov:sitewide-search-api
    params:
    - size
    - from
  - api: cancer-gov:r4r-api
    params:
    - size
    - from
  response_fields: null
  note: Derived from declared parameters in the specs. No service publishes a total-count or next-link
    convention in a schema, so page-exhaustion has to be inferred from a short result set.
field_expansion:
  supported: true
  note: The Clinical Trials Search API documents include/exclude query parameters for sparse fieldsets.
    The GDC exposes the equivalent through GraphQL field selection at https://api.gdc.cancer.gov/v0/graphql.
    The other services offer no projection controls.
metadata:
  supported: false
  note: No service exposes a customer-writable metadata bag on its resources.
request_id:
  supported: false
  note: No X-Request-Id, X-Correlation-Id or traceparent header was returned on any live response probed
    on 2026-09-05 (webapis.cancer.gov, api.seer.cancer.gov, api.gdc.cancer.gov, api-evsrest.nci.nih.gov).
    There is no documented way for a caller to quote a request back to NCI support.
versioning:
  style: path segment, per service
  cross_link: lifecycle/cancer-gov-lifecycle.yml
error_envelope:
  style: vendor-specific, three incompatible shapes
  rfc9457: false
  cross_link: errors/cancer-gov-problem-types.yml
rate_limit_signaling:
  headers: []
  status_on_exhaustion: null
  note: No X-RateLimit-*, RateLimit-* or Retry-After header was observed on any live response. SEER publishes
    a numeric limit in its terms of service but signals nothing at runtime, so an agent cannot see itself
    approaching the ceiling.
  cross_link: rate-limits/cancer-gov-rate-limits.yml
reversibility:
  grade: none
  supported: false
  note: 'There is a real write surface — 84 mutating operations — and not one reversal path. The destructive
    operations are plain deletes with no soft-delete, no restore and no stated recovery window: SEER exposes
    DELETE /rest/staging/{algorithm}, DELETE /rest/hcpcs/code/{code}, DELETE /rest/rx/{version}/delete/{id},
    DELETE /rest/disease/{version}/delete/{id} and DELETE /rest/glossary/{version}/delete/{id}; MoDaC
    exposes POST /deleteCollection, POST /delete/datafile and POST /deletePredictions. MoDaC''s retryUpload
    and retryDownload are retry operations on a transfer task, not reversals of a completed write. No
    documentation states any window in which a delete can be undone, so no window is recorded here.'
  surfaces:
  - api: cancer-gov:seer-api
    write_operations: 53
    reversal_operation: null
    window: null
  - api: cancer-gov:modac-api
    write_operations: 29
    reversal_operation: null
    window: null
  - api: cancer-gov:evs-api
    write_operations: 2
    reversal_operation: null
    window: null
  - api: cancer-gov:gdc-api
    write_operations: null
    reversal_operation: null
    window: null
    note: GDC submission is a write surface but publishes no OpenAPI, so its operation count cannot be
      derived.
dry_run_mode:
  supported: false
  note: No operation declares a dry-run, validate-only or preview mode in any of the eight specs.