Automated API Documentation & SDK Generator Agent

Problem Statement

Modern engineering teams face a persistent "documentation debt" cycle. In high-velocity startups, the underlying codebase and API endpoints evolve daily, but documentation is often an afterthought, leading to outdated Swagger files and broken code examples. This creates a friction-filled developer experience for external partners and internal frontend teams. When documentation lags behind code, support tickets increase, integration times double, and the perceived reliability of the product drops.

Similar to how a Customer Support Triage Agent reduces manual ticket handling, this agent automates the technical overhead of API maintenance. The core issue is that maintaining high-quality, idiomatic SDKs (Software Development Kits) in multiple languages (Python, TypeScript, Go) is manually intensive. A developer must update the backend logic, then manually update the OpenAPI specification, then manually rewrite the "Getting Started" guides, and finally push updates to various client libraries. This manual workflow is prone to human error—omitting a new required header or mislabeling a parameter type. For a startup with 5-10 developers, dedicating 20% of engineering time to "documentation maintenance" is an expensive waste of talent that should be focused on building core features. We need an agent that sits within the CI/CD pipeline to bridge the gap between the raw source code and the developer-facing documentation portal.

What the Agent Does/Doesn't Do

• Does: Scans repository changes to detect API schema updates; automatically generates/updates OpenAPI (Swagger) specs; generates idiomatic SDKs in TypeScript and Python; writes human-readable "Changelog" summaries for every version update.
• Doesn't: Write high-level architectural blog posts; handle authentication logic implementation; fix bugs in the underlying API code; interact directly with end-users for support.

Workflow

1. Trigger: GitHub Action triggers the agent upon a PR merge to the main branch.
2. Schema Extraction: Agent analyzes updated controllers/routes to extract types, parameters, and response objects.
   • Input: Git Diff + Source Code. Output: Updated openapi.yaml.
3. SDK Synthesis: Agent uses the updated spec to generate client libraries with proper typing and retry logic.
   • Input: openapi.yaml. Output: TS/Python SDK source code.
4. Example Generation: Agent generates "Copy-Paste" code snippets for common use cases based on the new schema. This functions much like a Document Q&A Agent by interpreting technical structures to provide immediate answers to developer queries.
   • Input: SDK code. Output: examples.md.
5. Documentation Sync: Agent pushes the updated spec and examples to a developer portal (e.g., ReadMe or Mintlify).
   • Input: Final assets. Output: Live documentation URL update.

Tool Stack

• Orchestration: LangGraph (Self-hosted or Cloud) - $0-$99/mo.
• LLM: Claude 3.5 Sonnet (Best for code generation/analysis) - ~$15/1M tokens.
• SDK Generation Engine: [VERIFY TOOL: Liblab] or OpenAPITools Generator (Open Source).
• Documentation Hosting: [VERIFY TOOL: Mintlify] - $150/mo (Startup plan).
• Version Control: GitHub Actions - Free tier.

Prompt Skeletons

### Prompt 1: Schema Extractor
Role: Senior Backend Architect
Task: Analyze the following Git Diff from a [Framework: e.g., FastAPI/Express] project. 
Identify new endpoints, changes in request headers, and modifications to JSON response schemas.
Output a valid OpenAPI 3.0 specification snippet that reflects these changes.
Context: {{git_diff}}
Rules: Ensure all types are strictly mapped (e.g., UUIDs as strings with format 'uuid').

### Prompt 2: SDK Idiomatic Refiner
Role: Senior Polyglot Developer
Task: Review the auto-generated SDK code for {{language}}. 
Ensure the code follows community best practices: 
- Use Promises/Async-Await for TS.
- Use Type Hints and Pydantic models for Python.
- Add docstrings to every method explaining the parameters based on the OpenAPI description.
Input Code: {{raw_sdk_code}}

### Prompt 3: Changelog Generator
Role: Technical Writer
Task: Compare the old OpenAPI spec with the new version.
Generate a "What's New" summary for developers. 
Categorize changes into: [Breaking Changes], [New Features], [Deprecations].
Keep the tone professional and concise.
Old Spec: {{old_spec}}
New Spec: {{new_spec}}

Success Metrics

• Time-to-Docs: Reduction in time between code merge and documentation update (Target: < 5 minutes).
• SDK Parity: 100% match between API endpoints and SDK methods.
• Support Reduction: Decrease in "How-to" or "Broken Integration" tickets by 30% QoQ.