Plinth Us Grants Data Authentication

generated: '2026-08-14'
method: searched
source: https://data.useplinth.com/developers#auth
corroboration:
  - openapi/plinth-us-grants-data-openapi.json          # components.securitySchemes.ApiKeyAuth
  - https://data.useplinth.com/.well-known/api-onboarding
  - https://data.useplinth.com/.well-known/oauth-authorization-server
derived_baseline: derive-authentication.py (2026-08-14) — upgraded to `searched` with the docs and onboarding descriptor.
checked: '2026-08-14'

summary:
  types: [apiKey, oauth2]
  api_key_in: [header]
  note: >-
    TWO independent auth systems on one host, and they do not overlap. The REST API takes a static
    API key in a header. The MCP connector takes OAuth 2.1 with PKCE and dynamic client
    registration. A REST key will not authenticate the connector and an OAuth token is not
    documented for REST. One operation — GET /api/search — is deliberately unauthenticated.

schemes:
  - name: ApiKeyAuth
    surface: REST (https://data.useplinth.com/api)
    type: apiKey
    in: header
    parameter: X-API-Key
    alternative_parameter: Authorization
    alternative_form: 'Bearer <key>'
    alternative_evidence: >-
      "Send your key in an X-API-Key header (or as a Authorization: Bearer token — both work)"
      (/developers#auth). NOTE: only X-API-Key is declared in the OpenAPI — the Bearer form is
      documented but not in the contract, so a generated client will only know the header form.
    token_prefix: plinth_sk_
    token_prefix_source: >-
      /developers#auth ("it starts plinth_sk_") and /.well-known/api-onboarding
      (authentication.methods[0].tokenPrefix).
    env_var: PLINTH_API_KEY
    env_var_source: /.well-known/api-onboarding (authentication.methods[0].env)
    applied: global
    applied_evidence: 'Root-level `security: [{ApiKeyAuth: []}]` in the OpenAPI, with a per-operation override on searchOrganizations.'
    issuance:
      mechanism: console-only
      url: https://data.useplinth.com/account
      programmatic: false
      cost: free tier requires no card
      sign_in: Google sign-in or an email link
      one_time_display: true
      keys_per_account: 1
      note: >-
        "The REST key is minted by a signed-in human at /account (one key per account, rotatable,
        shown once). There is no programmatic issue endpoint." — /.well-known/api-onboarding.
    rotation:
      supported: true
      url: https://data.useplinth.com/account
      semantics: immediate-revoke
      note: '"Rotating retires the previous key immediately." No overlap window — plan for a hard cutover.'
    ttl: none
    handling_guidance: >-
      "Keys are secrets — keep them server-side, never in browser JavaScript, a mobile binary or a
      committed file." (/developers#auth)
    sources:
      - https://data.useplinth.com/developers#auth
      - openapi/plinth-us-grants-data-openapi.json

  - name: ConnectorOAuth
    surface: MCP (https://data.useplinth.com/api/connector/mcp)
    type: oauth2
    profile: OAuth 2.1 (authorization_code + PKCE S256), public client
    declared_in_openapi: false
    declared_in_openapi_note: >-
      The REST OpenAPI does not model this scheme — correctly, since it protects a different
      surface. It is discoverable only from the RFC 8414 metadata document.
    metadata: well-known/plinth-us-grants-data-oauth-authorization-server.json
    protected_resource_metadata: well-known/plinth-us-grants-data-oauth-protected-resource.json
    issuer: https://data.useplinth.com
    authorization_endpoint: https://data.useplinth.com/oauth/authorize
    token_endpoint: https://data.useplinth.com/oauth/token
    registration_endpoint: https://data.useplinth.com/oauth/register
    dynamic_client_registration: true
    grant_types: [authorization_code, refresh_token]
    pkce: S256
    token_endpoint_auth_methods: [none]
    bearer_methods: [header]
    scopes: [plinth:read]
    see: scopes/plinth-us-grants-data-scopes.yml
    token_ttl: short-lived; refresh_token grant supported
    revocation: 'Remove the connector in the assistant, or revoke from https://data.useplinth.com/account.'
    challenge_observed:
      url: https://data.useplinth.com/api/connector/mcp
      status: 401
      header: >-
        www-authenticate: Bearer error="invalid_token", error_description="No authorization
        provided", resource_metadata="https://data.useplinth.com/.well-known/oauth-protected-resource"
      checked: '2026-08-14'
    sources:
      - https://data.useplinth.com/connect
      - https://data.useplinth.com/.well-known/oauth-authorization-server

anonymous_surface:
  operation: searchOrganizations
  path: GET /api/search
  security: []
  metered: false
  evidence: >-
    Per-operation `security: []` in the OpenAPI overrides the global requirement, and the spec says
    so in prose: "**No API key required and not metered.**" Verified live 2026-08-14: GET
    /api/search?q=barancik returned 200 with a result body and no auth header sent.
  significance: >-
    Rare and agent-friendly. Entity resolution — the step that must precede every other call when
    you have a name rather than an EIN — is free, unkeyed and unmetered. An agent can resolve
    "Barancik Foundation" to EIN 363442474 and a canonical URL before it needs any credential at
    all. Plinth's own onboarding descriptor calls this "the intended first call."

agent_readiness_notes:
  can_an_agent_self_provision: false
  blocker: >-
    A human must sign in at /account to mint the REST key, and must hold the For consultants plan
    before the MCP consent step can succeed. The provider documents both as gaps in its own
    onboarding descriptor rather than leaving an agent to discover them at a 401.
  strongest_signal: >-
    The credential requirements are published as MACHINE-READABLE data, not prose: token prefix,
    env var name, rotation semantics, one-time display, plan gates and the registration mechanisms
    all live in /.well-known/api-onboarding. Very few providers in the catalog publish this.