API Evangelist enhancements for the BudgetPixel API

overlay: 1.0.0
info:
  title: API Evangelist enhancements for the BudgetPixel API
  version: 1.0.0
extends: ../openapi/budgetpixel-openapi.yaml
x-provenance:
  generated: '2026-08-28'
  method: generated
  source: >-
    Derived from artifacts in this repo -- conventions/budgetpixel-conventions.yml,
    errors/budgetpixel-problem-types.yml, rate-limits/budgetpixel-rate-limits.yml,
    lifecycle/budgetpixel-lifecycle.yml, mcp/budgetpixel-tool-crosswalk.yml. Adds only
    machine-readable restatements of facts BudgetPixel already publishes in prose; it never
    invents contract behaviour and it never mutates the original spec.
actions:
  - target: $.info
    description: Record the published maturity and the plan gate as structured extensions rather than prose.
    update:
      x-maturity: private-beta
      x-plan-gate:
        required_plans: [Premium, Pro, Ultra]
        additional: private beta access required to mint an API key
        source: https://docs.budgetpixel.com/introduction#availability
      x-support-email: support@budgetpixel.com

  - target: $.info
    description: >-
      Surface the rate-limit contract as data. The numbers and headers are stated in
      info.description and at /concepts/rate-limits, but nothing in the spec is readable by a
      client generator; the X-RateLimit trio was also observed live on a 401.
    update:
      x-rate-limits:
        headers: [X-RateLimit-Limit, X-RateLimit-Remaining, X-RateLimit-Reset, Retry-After]
        exhaustion_status: 429
        reset_semantics: seconds-until-window-reset
        buckets:
          - scope: per-api-key
            limit: 600
            window: 60s
          - scope: per-source-ip
            limit: 1200
            window: 60s
          - scope: per-account
            limit: 60
            window: 60s
            applies_to: uploadMedia
        source: https://docs.budgetpixel.com/concepts/rate-limits

  - target: $.info
    description: >-
      Record the reversibility posture. The API has 49 charged write operations and no DELETE
      verb anywhere -- no cancel, refund, void or undo. This is the fact an agent most needs
      before it acts, and it is currently only inferable from the absence of endpoints.
    update:
      x-reversibility:
        grade: absent
        reversal_operations: []
        window: null
        note: >-
          No submitted job can be cancelled and no successful generation can be refunded.
          Public social posts (createPost) have no API delete. The only mitigation is
          preventative: quote with estimateCost before committing.
      x-idempotency:
        supported: false
        note: >-
          No idempotency key. Combined with x-reversibility, an ambiguous timeout on a
          generation POST is unsafe to retry -- it may create a second charged job that
          cannot be undone, and REST publishes no history endpoint to check first.

  - target: $.info
    description: Point at the machine-readable agent surfaces the provider serves off-spec.
    update:
      x-agent-surfaces:
        mcp_server: https://mcp.budgetpixel.com/mcp
        mcp_transport: streamable-http
        mcp_auth: OAuth 2.1 + PKCE (S256), Google SSO
        agent_card: https://docs.budgetpixel.com/.well-known/agent-card.json
        agent_skill: https://docs.budgetpixel.com/.well-known/agent-skills/budgetpixel/skill.md
        llms_txt: https://docs.budgetpixel.com/llms.txt
        crosswalk: ../mcp/budgetpixel-tool-crosswalk.yml

  - target: $.components.schemas.Error
    description: Name the error envelope standard explicitly so clients stop guessing at RFC 9457.
    update:
      x-error-format: vendor-json
      x-rfc9457: false
      x-envelope-warning: >-
        Content-moderation blocks return a DIFFERENT, flatter shape on the same 400 status,
        where `error` is a bare string rather than this object. See ModerationBlocked.

  - target: $.components.schemas.ModerationBlocked
    description: Flag the divergent envelope on the schema itself.
    update:
      x-alternate-envelope: true
      x-retryable: true
      x-retry-guidance: >-
        Retryable after changing the prompt or input media. Not an auth, quota or account
        failure -- branch on restriction_reason, which is stable.

  - target: $.paths['/cost'].post
    description: Mark the cost endpoint as the dry-run affordance for the whole API.
    update:
      x-dry-run: true
      x-agent-guidance: >-
        Call this before any generation. It is computed by the same code that bills, so it
        never disagrees with the charge. exact:false means the returned credits are a ceiling.

  - target: $.paths['/posts'].post
    description: Mark the one operation with a public, irreversible, third-party-visible consequence.
    update:
      x-consequence: public-irreversible
      x-credits: 10
      x-agent-guidance: >-
        Publishes to a PUBLIC community feed and cannot be undone through the API. Require
        explicit human confirmation before calling. A post later hidden by content review is
        not refunded.

  - target: $.paths['/uploads'].post
    description: Record the dedicated upload cap and the input lifetime.
    update:
      x-rate-limit:
        scope: per-account
        limit: 60
        window: 60s
        reason: free and unmetered
      x-output-ttl: ~24h