OpenAPI Specification Generator

note

For a deep-dive into database-first OpenAPI design — type mapping, the Base/Create/Full component triad, and how schema constraints inform path structure — see Your Database Is Already an API.

TalkingSchema's AI copilot derives a production-grade OpenAPI 3.1 specification from your entity relationship diagram. Every table becomes a components/schema, every relationship informs response nesting, and standard CRUD paths are generated with typed request bodies, response envelopes, and pagination parameters. The AI explicitly calls out assumptions it makes — such as inferred endpoint semantics — so you can correct them before committing to the contract.

Outputs are provided as YAML or JSON code blocks, with an option to download as a .yaml or .json file coming soon

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How to Generate an OpenAPI Spec

Standard CRUD spec

Generate an OpenAPI 3.1 YAML spec for CRUD endpoints based on this schema.
For each resource: GET /{resource} (list with pagination), POST /{resource},
GET /{resource}/{id}, PATCH /{resource}/{id}, DELETE /{resource}/{id}.
Include components/schemas with all field types, nullable flags, and enums.

Selective endpoints

Generate OpenAPI 3.1 paths only for: suppliers (read-only), products
(full CRUD), and purchase_orders (create + read, no update or delete).
Explain any assumptions about resource nesting.

With authentication

Generate an OpenAPI 3.1 spec with Bearer token authentication applied
to all endpoints. Include a securitySchemes component and apply
security: [bearerAuth: []] globally.

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Example Output

Using the Global Sustainable Supply Chain (GSSC) schema — showing the suppliers and products resources:

openapi: "3.1.0"
info:
  title: Global Sustainable Supply Chain API
  version: "1.0.0"
  description: >
    REST API for managing suppliers, products, purchase orders, shipments,
    and inventory across a multi-warehouse supply chain network.

servers:
  - url: https://api.example.com/v1

security:
  - bearerAuth: []

components:
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: JWT

  schemas:
    CarbonTier:
      type: string
      enum: [A, B, C, D]
      description: Supplier sustainability certification tier (A = highest, D = lowest)

    SupplierBase:
      type: object
      properties:
        company_name:
          type: string
          maxLength: 200
        country:
          type: string
          maxLength: 100
        carbon_tier:
          $ref: "#/components/schemas/CarbonTier"
        certification:
          type: string
          maxLength: 100
          nullable: true
        is_active:
          type: boolean
          default: true

    Supplier:
      allOf:
        - $ref: "#/components/schemas/SupplierBase"
        - type: object
          properties:
            supplier_id:
              type: string
              format: uuid
              readOnly: true
            created_at:
              type: string
              format: date-time
              readOnly: true
            updated_at:
              type: string
              format: date-time
              readOnly: true
          required:
            - supplier_id
            - company_name
            - country
            - carbon_tier
            - created_at
            - updated_at

    SupplierCreate:
      allOf:
        - $ref: "#/components/schemas/SupplierBase"
      required:
        - company_name
        - country
        - carbon_tier

    ProductBase:
      type: object
      properties:
        sku:
          type: string
          maxLength: 50
        name:
          type: string
          maxLength: 200
        category:
          type: string
          maxLength: 100
        unit_weight_kg:
          type: number
          format: double
          nullable: true
        unit_cost_usd:
          type: number
          format: double
          minimum: 0
        carbon_intensity_score:
          type: number
          format: double
          minimum: 0
          maximum: 999.99
          nullable: true
          description: CO₂ emissions in kg per unit produced
        supplier_id:
          type: string
          format: uuid
        is_active:
          type: boolean
          default: true

    Product:
      allOf:
        - $ref: "#/components/schemas/ProductBase"
        - type: object
          properties:
            product_id:
              type: string
              format: uuid
              readOnly: true
            created_at:
              type: string
              format: date-time
              readOnly: true
            updated_at:
              type: string
              format: date-time
              readOnly: true

    PaginatedSuppliers:
      type: object
      properties:
        data:
          type: array
          items:
            $ref: "#/components/schemas/Supplier"
        total:
          type: integer
        page:
          type: integer
        per_page:
          type: integer

    ErrorResponse:
      type: object
      properties:
        error:
          type: string
        message:
          type: string
      required:
        - error

paths:
  /suppliers:
    get:
      operationId: listSuppliers
      summary: List all suppliers
      tags: [Suppliers]
      parameters:
        - name: page
          in: query
          schema:
            type: integer
            default: 1
        - name: per_page
          in: query
          schema:
            type: integer
            default: 20
            maximum: 100
        - name: carbon_tier
          in: query
          schema:
            $ref: "#/components/schemas/CarbonTier"
        - name: is_active
          in: query
          schema:
            type: boolean
      responses:
        "200":
          description: Paginated list of suppliers
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/PaginatedSuppliers"
    post:
      operationId: createSupplier
      summary: Create a new supplier
      tags: [Suppliers]
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/SupplierCreate"
      responses:
        "201":
          description: Supplier created
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Supplier"
        "400":
          description: Validation error
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/ErrorResponse"

  /suppliers/{supplier_id}:
    parameters:
      - name: supplier_id
        in: path
        required: true
        schema:
          type: string
          format: uuid
    get:
      operationId: getSupplier
      summary: Get supplier by ID
      tags: [Suppliers]
      responses:
        "200":
          description: Supplier record
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Supplier"
        "404":
          description: Not found
    patch:
      operationId: updateSupplier
      summary: Partially update a supplier
      tags: [Suppliers]
      requestBody:
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/SupplierBase"
      responses:
        "200":
          description: Updated supplier
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Supplier"
    delete:
      operationId: deleteSupplier
      summary: Delete a supplier
      tags: [Suppliers]
      responses:
        "204":
          description: Deleted successfully

---

Customizing the Output

Requirement	Prompt addition
JSON instead of YAML	"Output as JSON instead of YAML"
Nested resource paths	"Use nested paths: /suppliers/{id}/products instead of flat /products"
Exclude delete endpoints	"Do not generate DELETE paths for any resource"
Add response envelope	"Wrap all responses in a data/meta envelope: { data: T, meta: { request_id: string } }"
OpenAPI 3.0 instead of 3.1	"Target OpenAPI 3.0.3 for compatibility with AWS API Gateway"
Add examples	"Include a realistic example object for each schema component"

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Frequently Asked Questions

Does the spec include relationship endpoints?

By default, TalkingSchema generates flat resource endpoints. Ask explicitly for nested paths: "Generate nested endpoints for purchase_order_items under /purchase-orders/{id}/items."

Can the spec be used with code generators?

Yes. The output is valid OpenAPI 3.1 YAML that works with openapi-generator, oapi-codegen (Go), openapi-typescript, and Swagger Codegen to scaffold client SDKs and server stubs.

Does the AI explain its assumptions?

Yes. The AI notes assumptions it makes about resource naming, HTTP method semantics, and relationships. Review and adjust these before using the spec as a binding API contract.