> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fiveninelabs.com/llms.txt
> Use this file to discover all available pages before exploring further.

# The ledger — every settle cites its run and receipts



## OpenAPI

````yaml /api-reference/openapi.yaml get /usage
openapi: 3.1.0
info:
  title: Five Nine Agent API
  version: '2026-08-26'
  description: >
    Live catalogs from the open web, under signed receipts.

    Conventions (versioning via the dated `fn-version` header, request IDs,

    idempotency, rate limits, pagination, money) are documented across this

    reference; the error envelope at https://docs.fiveninelabs.com/errors; the

    event vocabulary at https://docs.fiveninelabs.com/guides/events; webhooks at

    https://docs.fiveninelabs.com/guides/webhooks.


    Honesty marker: operations tagged `x-fn-status: planned` are specced but NOT

    yet served by the live API — on any method they answer 501 not_implemented
    with

    a `surface` member naming what is missing, never 404. Everything unmarked is

    live. The changelog says when a planned surface ships.
servers:
  - url: https://api.fiveninelabs.com/v1
security:
  - bearerKey: []
paths:
  /usage:
    get:
      summary: The ledger — every settle cites its run and receipts
      parameters:
        - $ref: '#/components/parameters/FnVersion'
        - $ref: '#/components/parameters/Limit'
        - $ref: '#/components/parameters/After'
        - name: from
          in: query
          schema:
            type: string
            format: date
        - name: key
          in: query
          schema:
            type: string
            description: filter by key id
      responses:
        '200':
          description: Page of ledger entries
          content:
            application/json:
              schema:
                type: object
                properties:
                  data:
                    type: array
                    items:
                      $ref: '#/components/schemas/LedgerEntry'
                  has_more:
                    type: boolean
                  next:
                    type: string
        '401':
          $ref: '#/components/responses/Unauthorized'
        '403':
          $ref: '#/components/responses/Forbidden'
components:
  parameters:
    FnVersion:
      name: fn-version
      in: header
      required: false
      schema:
        type: string
        example: '2026-08-26'
      description: >-
        Dated API version; defaults to the account pin. Honesty note: with one
        version in existence the gateway echoes any value back as effective
        WITHOUT validating it — validation against the known-versions set is
        planned, so send only real dated versions from
        https://docs.fiveninelabs.com/changelog
    Limit:
      name: limit
      in: query
      schema:
        type: integer
        minimum: 1
        maximum: 100
        default: 25
    After:
      name: after
      in: query
      schema:
        type: string
        description: opaque cursor from a prior page's next
  schemas:
    LedgerEntry:
      type: object
      required:
        - at
        - kind
        - amount_usd
      properties:
        at:
          type: string
          format: date-time
        kind:
          type: string
          description: >-
            grant | reserve | settle | release | adjust — grant and release
            positive, settle negative, adjust either (its description says why)
        run_id:
          type: string
        run_type:
          type: string
        description:
          type: string
        rows:
          type: integer
        receipts:
          type: string
          description: e.g. 3 of 3
        amount_usd:
          type: number
          description: signed; grants positive
    Error:
      type: object
      required:
        - error
      properties:
        error:
          type: object
          required:
            - type
            - code
            - message
            - doc_url
            - request_id
          properties:
            type:
              type: string
            code:
              type: string
            message:
              type: string
            doc_url:
              type: string
              format: uri
            request_id:
              type: string
          additionalProperties: true
  responses:
    Unauthorized:
      description: 401 invalid_key | key_revoked — key missing, unknown, or revoked
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    Forbidden:
      description: >-
        403 missing_scope — or a cap forbids this (session_cap_exceeded |
        monthly_cap_exceeded; caps are permissions, not rates)
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
  securitySchemes:
    bearerKey:
      type: http
      scheme: bearer
      description: 'fn_live_… or fn_test_… — Authorization: Bearer'

````