APIs.io Synthesis API

openapi: 3.2.0
info:
  title: APIs.io Synthesis API
  description: |-
    Decision-grade composites over the catalog — provider comparison, gap analysis, catalog change feed, and recommended-stack design. Pro.

    This is the Synthesis surface of the [APIs.io API](https://apis.io/api/v1) — one of 17 contracts split from the full API by tag, each documented and governed on its own. See the APIs.json index for the whole set.
  version: 1.5.0
  contact:
    name: API Evangelist
    url: https://apis.io
  license:
    name: CC BY 4.0
    url: https://creativecommons.org/licenses/by/4.0/
servers:
  - url: https://apis.io/api/v1
    description: Production server.
tags:
  - name: Synthesis
    description: Decision-grade composites over the catalog — provider comparison, gap analysis, catalog change feed, and recommended-stack design. Pro.
paths:
  /compare:
    get:
      operationId: compareProviders
      x-tier: pro
      x-mcp-tool: compare_providers
      security: []
      tags:
        - Synthesis
      summary: Compare providers side by side (Pro).
      description: Compares 2+ providers — composite/band, per-facet leaders, and an artifact-coverage matrix. Pro tier.
      parameters:
        - name: providers
          in: query
          required: true
          description: Comma-separated provider slugs to compare (2+).
          schema:
            type: string
            maxLength: 1024
      responses:
        "200":
          description: Side-by-side comparison of the requested providers.
          content:
            application/json:
              schema:
                type: object
                additionalProperties: true
          headers:
            ratelimit-policy:
              $ref: "#/components/headers/RateLimitPolicy"
            x-ratelimit-tier:
              $ref: "#/components/headers/RateLimitTier"
            x-ratelimit-limit:
              $ref: "#/components/headers/RateLimitLimit"
            x-ratelimit-window:
              $ref: "#/components/headers/RateLimitWindow"
        "400":
          $ref: "#/components/responses/BadRequest"
        "402":
          $ref: "#/components/responses/UpgradeRequired"
  /gaps:
    get:
      operationId: gapAnalysis
      x-tier: pro
      x-mcp-tool: gap_analysis
      security: []
      tags:
        - Synthesis
      summary: Artifact + score gap analysis for a provider or stack (Pro).
      description: For each provider — the high-value artifacts it lacks, what its peers commonly publish but it lacks, and its score vs the peer median — plus stack-level gaps across the set. Pro tier.
      parameters:
        - name: providers
          in: query
          required: true
          description: Comma-separated provider slugs (1+). Multiple = treat as a stack.
          schema:
            type: string
            maxLength: 1024
        - name: min_share
          in: query
          description: Peer-share threshold for a gap (0–1, default 0.25).
          schema:
            type: number
            maximum: 1000000000
      responses:
        "200":
          description: Per-provider and stack-level gaps.
          content:
            application/json:
              schema:
                type: object
                additionalProperties: true
          headers:
            ratelimit-policy:
              $ref: "#/components/headers/RateLimitPolicy"
            x-ratelimit-tier:
              $ref: "#/components/headers/RateLimitTier"
            x-ratelimit-limit:
              $ref: "#/components/headers/RateLimitLimit"
            x-ratelimit-window:
              $ref: "#/components/headers/RateLimitWindow"
        "400":
          $ref: "#/components/responses/BadRequest"
        "402":
          $ref: "#/components/responses/UpgradeRequired"
  /changes:
    get:
      operationId: whatsChanged
      x-tier: pro
      x-mcp-tool: whats_changed
      security: []
      tags:
        - Synthesis
      summary: What changed in the catalog since a date (Pro).
      description: Providers added/updated since a date, plus rating movement (up/down) from the latest scoring build. Pro tier.
      parameters:
        - name: since
          in: query
          required: true
          description: Cutoff date, YYYY-MM-DD.
          schema:
            type: string
            format: date
            maxLength: 10
        - $ref: "#/components/parameters/Limit"
      responses:
        "200":
          description: Catalog changes since the given date.
          content:
            application/json:
              schema:
                type: object
                additionalProperties: true
          headers:
            ratelimit-policy:
              $ref: "#/components/headers/RateLimitPolicy"
            x-ratelimit-tier:
              $ref: "#/components/headers/RateLimitTier"
            x-ratelimit-limit:
              $ref: "#/components/headers/RateLimitLimit"
            x-ratelimit-window:
              $ref: "#/components/headers/RateLimitWindow"
        "400":
          $ref: "#/components/responses/BadRequest"
        "402":
          $ref: "#/components/responses/UpgradeRequired"
  /stack:
    get:
      operationId: recommendStack
      x-tier: free
      x-mcp-tool: recommend_stack
      x-agent-skill: assemble-api-stack
      tags:
        - Synthesis
      summary: Design a recommended API stack per capability.
      description: Decompose a domain into capabilities, then get the best-rated catalog provider per capability assembled into a stack. FREE returns a preview (top pick per capability); PRO returns alternatives, per-pick artifact gaps, and an exportable APIs.json + Arazzo hint.
      parameters:
        - name: capabilities
          in: query
          required: true
          description: Comma-separated capabilities the stack needs, e.g. `payments,email,identity,observability`.
          schema:
            type: string
            maxLength: 1024
        - name: region
          in: query
          description: Optional region slug to prefer, e.g. `europe`.
          schema:
            type: string
            maxLength: 1024
      responses:
        "200":
          description: A recommended stack (preview for free callers; full for Pro).
          content:
            application/json:
              schema:
                type: object
                additionalProperties: true
          headers:
            ratelimit-policy:
              $ref: "#/components/headers/RateLimitPolicy"
            x-ratelimit-tier:
              $ref: "#/components/headers/RateLimitTier"
            x-ratelimit-limit:
              $ref: "#/components/headers/RateLimitLimit"
            x-ratelimit-window:
              $ref: "#/components/headers/RateLimitWindow"
        "400":
          $ref: "#/components/responses/BadRequest"
      security: []
  /gaps/industry/{slug}:
    get:
      operationId: industryGapAnalysis
      x-tier: pro
      x-mcp-tool: industry_gap_analysis
      x-agent-skill: audit-api-estate
      security: []
      tags:
        - Synthesis
      summary: Artifact gaps across a whole industry.
      description: For an industry vertical, reports which valuable artifact types (MCP, Arazzo, Rules, Skills…) most member providers lack — where the vertical is under-served.
      parameters:
        - name: slug
          in: path
          required: true
          description: Industry slug (e.g. `financial-services`).
          schema:
            type: string
            maxLength: 1024
        - name: min_share
          in: query
          description: Coverage threshold below which a type counts as an industry gap (0–1, default 0.5).
          schema:
            type: number
            maximum: 1000000000
      responses:
        "200":
          description: The industry's valuable-artifact coverage and gaps.
          content:
            application/json:
              schema:
                type: object
                additionalProperties: true
          headers:
            ratelimit-policy:
              $ref: "#/components/headers/RateLimitPolicy"
            x-ratelimit-tier:
              $ref: "#/components/headers/RateLimitTier"
            x-ratelimit-limit:
              $ref: "#/components/headers/RateLimitLimit"
            x-ratelimit-window:
              $ref: "#/components/headers/RateLimitWindow"
        "402":
          $ref: "#/components/responses/UpgradeRequired"
        "404":
          $ref: "#/components/responses/NotFound"
  /stack/export:
    get:
      operationId: exportStack
      x-tier: pro
      x-mcp-tool: export_stack
      x-agent-skill: assemble-api-stack
      security: []
      tags:
        - Synthesis
      summary: Export a designed stack as APIs.json.
      description: Given a set of capabilities, returns the designed stack as an adoptable APIs.json document (with an Arazzo hint) the team can commit.
      parameters:
        - name: capabilities
          in: query
          required: true
          description: Comma-separated capabilities the stack needs, e.g. `payments,email,identity`.
          schema:
            type: string
            maxLength: 1024
        - name: region
          in: query
          description: Optional region slug to prefer.
          schema:
            type: string
            maxLength: 1024
      responses:
        "200":
          description: The exportable stack.
          content:
            application/json:
              schema:
                type: object
                additionalProperties: true
          headers:
            ratelimit-policy:
              $ref: "#/components/headers/RateLimitPolicy"
            x-ratelimit-tier:
              $ref: "#/components/headers/RateLimitTier"
            x-ratelimit-limit:
              $ref: "#/components/headers/RateLimitLimit"
            x-ratelimit-window:
              $ref: "#/components/headers/RateLimitWindow"
        "400":
          $ref: "#/components/responses/BadRequest"
        "402":
          $ref: "#/components/responses/UpgradeRequired"
components:
  parameters:
    Limit:
      name: limit
      in: query
      description: Items per page.
      schema:
        type: integer
        minimum: 1
        maximum: 100
        default: 25
  schemas:
    Problem:
      type: object
      description: |
        A Problem Details object per [RFC 9457](https://www.rfc-editor.org/rfc/rfc9457).
        Served as `application/problem+json`. Extension members (e.g. `parameter`) may be
        added alongside the standard fields.
      properties:
        type:
          type: string
          format: uri
          default: about:blank
          description: A URI identifying the problem type; dereferences to human-readable docs.
          examples:
            - https://apis.io/problems/invalid-parameter
          maxLength: 2048
        title:
          type: string
          description: A short, human-readable summary of the problem type.
          examples:
            - Invalid parameter
          maxLength: 1024
        status:
          type: integer
          minimum: 100
          maximum: 599
          description: The HTTP status code, repeated for convenience.
          examples:
            - 400
        detail:
          type: string
          description: A human-readable explanation specific to this occurrence.
          maxLength: 20000
          examples:
            - "`match` must be one of: any, all."
        instance:
          type: string
          format: uri-reference
          description: A URI reference identifying the specific occurrence (typically the request path).
          maxLength: 2048
          examples:
            - /v1/search
        parameter:
          type: string
          description: Extension member — the offending query/path parameter, when applicable.
          maxLength: 1024
          examples:
            - match
      required:
        - type
        - title
        - status
      additionalProperties: true
  responses:
    UpgradeRequired:
      description: Payment Required — this operation needs a paid tier. Send a plan key in `X-API-Key`.
      content:
        application/problem+json:
          schema:
            $ref: "#/components/schemas/Problem"
          example:
            type: https://apis.io/problems/upgrade-required
            title: Upgrade required
            status: 402
            detail: This endpoint requires the Understanding or Influence plan.
            instance: /v1/ratings
      headers:
        ratelimit-policy:
          $ref: "#/components/headers/RateLimitPolicy"
        x-ratelimit-tier:
          $ref: "#/components/headers/RateLimitTier"
        x-ratelimit-limit:
          $ref: "#/components/headers/RateLimitLimit"
        x-ratelimit-window:
          $ref: "#/components/headers/RateLimitWindow"
    NotFound:
      description: Resource not found.
      content:
        application/problem+json:
          schema:
            $ref: "#/components/schemas/Problem"
          example:
            type: https://apis.io/problems/not-found
            title: Resource not found
            status: 404
            detail: No API found with aid `twilio:nope`.
            instance: /v1/apis/twilio:nope
      headers:
        ratelimit-policy:
          $ref: "#/components/headers/RateLimitPolicy"
        x-ratelimit-tier:
          $ref: "#/components/headers/RateLimitTier"
        x-ratelimit-limit:
          $ref: "#/components/headers/RateLimitLimit"
        x-ratelimit-window:
          $ref: "#/components/headers/RateLimitWindow"
    BadRequest:
      description: Malformed request (bad parameter value).
      content:
        application/problem+json:
          schema:
            $ref: "#/components/schemas/Problem"
          example:
            type: https://apis.io/problems/invalid-parameter
            title: Invalid parameter
            status: 400
            detail: "`match` must be one of: any, all."
            instance: /v1/search
            parameter: match
      headers:
        ratelimit-policy:
          $ref: "#/components/headers/RateLimitPolicy"
        x-ratelimit-tier:
          $ref: "#/components/headers/RateLimitTier"
        x-ratelimit-limit:
          $ref: "#/components/headers/RateLimitLimit"
        x-ratelimit-window:
          $ref: "#/components/headers/RateLimitWindow"
  headers:
    RateLimitPolicy:
      description: The quota and burst policy applied to this key, in the RFC 9745 RateLimit-Policy form.
      schema:
        type: string
        maxLength: 1024
      example: "\"quota\";q=500;w=86400, \"burst\";q=5;w=1"
    RateLimitTier:
      description: The tier the call was served at. Keyless callers are served `free`.
      schema:
        type: string
        enum:
          - free
          - pro
          - business
      example: free
    RateLimitLimit:
      description: Requests allowed in the current quota window.
      schema:
        type: integer
        maximum: 1000000
      example: 500
    RateLimitWindow:
      description: Length of the quota window, in seconds.
      schema:
        type: integer
        maximum: 1000000
      example: 86400
  securitySchemes:
    ApiKeyAuth:
      type: apiKey
      in: header
      name: X-API-Key
      description: Send a plan key to be served above the free tier. Keyless callers get the free tier; a call that needs a paid tier answers 402 rather than refusing the connection.