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

# The append-only credit audit trail



## OpenAPI

````yaml /api-reference/billing.json get /api/billing/ledger
openapi: 3.1.0
info:
  title: truscan billing
  version: 1.0.0
  description: >-
    Credits, metering and top-ups. Money is counted in MICRO-DOLLARS (millionths
    of a dollar) as integers everywhere, so $7.00 per 1,000 requests is exactly
    7,000 micros per request. Floats drift, and a billing system that drifts
    gets disputed. Every amount is accompanied by a pre-formatted display string
    so no client reimplements money formatting. All responses use the {success,
    result, message} envelope except health and the webhook.
servers:
  - url: https://api.truscan.co
    description: Production
security: []
paths:
  /api/billing/ledger:
    get:
      summary: The append-only credit audit trail
      parameters:
        - name: limit
          in: query
          schema:
            type: integer
            default: 50
            maximum: 200
      responses:
        '200':
          description: Ledger entries, newest first
          content:
            application/json:
              schema:
                type: object
                properties:
                  success:
                    type: boolean
                  message:
                    type: string
                  result:
                    type: array
                    items:
                      $ref: '#/components/schemas/LedgerEntry'
        '401':
          $ref: '#/components/responses/Failure'
components:
  schemas:
    LedgerEntry:
      type: object
      properties:
        id:
          type: integer
        delta_micros:
          type: integer
          description: Negative for usage, positive for grants and top-ups.
        balance_after_micros:
          type: integer
        kind:
          type: string
          enum:
            - grant
            - topup
            - usage
        reason:
          type: string
        created_at:
          type: string
          format: date-time
    Failure:
      type: object
      properties:
        success:
          type: boolean
          const: false
        message:
          type: string
          description: Written for a person.
        result:
          type: object
          properties:
            code:
              type: string
              enum:
                - insufficient_credits
                - payments_unavailable
                - invalid_amount
                - unauthorized
                - validation_failed
                - internal_error
                - upstream_unavailable
  responses:
    Failure:
      description: >-
        The envelope with success false. result carries the machine-readable
        code and nothing else.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Failure'

````