FMFansMetric API

Authentication

Auth

Authenticate API requests with an API key. Keys are scoped to an organization and carry a per-route permission set.

Passing the key

Send your API key with every request in one of two headers. Both behave the same way; the bearer form is recommended for tooling that already supports OAuth-style headers.

  • Authorization: Bearer fm_api_...
  • X-API-Key: fm_api_...

Permissions

Each API key has a role, and each role has a set of per-route permissions. If a key doesn't have the permission required by an endpoint, the request returns 403.

Permissions are named like api_chats_list, api_messages_send, api_tracking_links_create. Each endpoint reference page calls out the permission it requires.

Rate limits

Limits are enforced per organization — every key in an org shares the same window. Two windows are tracked independently: per-minute (default 1,000) and per-day (default 50,000). Either limit can trigger a 429.

Headroom is reported on every successful response inside _meta._rate_limits (remaining_minute, remaining_day).

Errors

Error responses use a flat { "error": "..." } body — no data and no _meta. The HTTP status reflects the failure class.

  • 400 — malformed request: bad query params, invalid body, unknown enum value
  • 401 — auth failed: missing, invalid, revoked, or expired API key. Does not consume a credit
  • 402 — your FansMetric organization has no active subscription (or is past due). Connect / repair billing in the FansMetric app
  • 403 — your API key role does not grant the per-route permission required by this endpoint
  • 404 — resource not found on OnlyFans or in FansMetric (depending on the route)
  • 413 — request body exceeds the 1 MiB limit applied to every authenticated route
  • 424 — the connected OnlyFans account is in sync_lost and cannot proxy upstream calls until the session is restored
  • 429 — per-organization rate limit exceeded (per-minute or per-day window). Back off until _meta._rate_limits.remaining_* recovers. Does not consume a credit
  • 5xx — upstream OnlyFans error, OF proxy error, or unhandled exception (5xx errors are captured by our error tracking)

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