---
title: OpenAPI Spec Generation
category: product
entity_type: skill
price: $15
canonical: https://forgehouse.ai/skills/openapi-spec-generation/
lang: en
hreflang_alt: https://forgehouse.ai/tr/skiller/openapi-spec-generation/
last_updated: 2026-06-20
---

# OpenAPI Spec Generation

> Generate and maintain OpenAPI 3.1 specifications from code, design-first specs, and validation…

Everything you need to author, generate, and validate OpenAPI 3.1 specifications that stay in sync with your code. It covers design-first specs, code-first generation from FastAPI and tsoa, and automated linting so your API contract becomes the single source of truth for docs, SDKs, mocks, and tests. No more drift between what the API says and what it does.

## Use cases
- Writing an API contract before any code (design-first)
- Generating a spec from existing FastAPI or Express code
- Linting and validating an OpenAPI document
- Generating client SDKs in TypeScript, Python, or Go
- Standing up Swagger UI or Redoc documentation portals
- Enforcing naming and security conventions across endpoints

## Benefits
- Eliminates drift by deriving SDKs, docs, and mocks from one canonical spec
- Lets frontend and backend build in parallel against an agreed contract
- Catches contract violations early with Spectral and Redocly linting in CI
- Documents every error code and auth scheme so consumers integrate without guesswork

## What’s included
- A full annotated OpenAPI 3.1 spec with schemas, parameters, responses, and examples
- Code-first templates for Python/FastAPI and TypeScript/tsoa
- Reusable $ref patterns for schemas, parameters, and shared error responses
- Spectral and Redocly lint rulesets with naming and security rules
- SDK generation commands for TypeScript, Python, and Go
- Security scheme definitions (Bearer JWT, API key) with per-endpoint requirements

## Who it’s for
For backend and platform engineers who treat the API contract as a product and want spec, code, and docs to never disagree.

## How it runs
Contract first, code second. The skill produces and enforces the API contract in this exact loop, so SDKs, docs and tests all derive from one source:
1. Decide the approach per project: design-first (spec written and agreed before code) for new APIs, code-first (FastAPI/Pydantic or tsoa decorators generating the spec) for existing services
2. Write the spec skeleton: info with version and rate limit docs, server list (production, staging, local), tags, then every path with operationId, summary, parameters and examples
3. Build the components layer for reuse: shared schemas referenced with $ref, common parameters (pagination, IDs), a single consistent Error schema with code, message, details and requestId used by every 4xx/5xx response
4. Lock down security in the spec itself: bearerAuth and apiKey schemes defined, a security requirement on every endpoint, sensitive fields marked readOnly, rate limit headers documented on 429 responses
5. Lint before anything ships: Spectral ruleset enforces operationIds, descriptions and naming conventions, Redocly validates examples and mime types, failures block the merge
6. Generate the downstream artifacts from the validated spec: TypeScript, Python or Go clients via openapi-generator, bundled docs via Redocly, and version every breaking change with a new path prefix while keeping operationIds stable

## FAQ
### We run Express, not FastAPI, am I covered?
Partly by templates, fully by method. The ready code-first templates target Python/FastAPI and TypeScript/tsoa, and generating a spec from existing Express code is a supported use case; the design-first authoring, $ref patterns, and Spectral/Redocly linting are framework-agnostic.

### How does it keep the spec from drifting away from the actual API?
By making the spec the single canonical source: SDKs, docs, and mocks are all derived from it, and Spectral plus Redocly rulesets run in CI to catch contract violations before merge. Drift stops being something you discover from angry API consumers.

### Does it write the API implementation for me?
No. It produces the contract, lint rules, SDK generation commands, and documentation portals, the endpoint logic behind that contract is still your code. It also targets OpenAPI 3.1, so legacy Swagger 2.0 documents need upgrading first.

## Price
$15, one-time, no subscription. VAT included.

Related guide: [AI code review and developer workflow](https://forgehouse.ai/guides/ai-code-review/)