OpenAI API Context Guide for AI Coding (llms.txt + Rules + MCP)

Build next-generation applications with GPT-4o, reasoning models (o1/o3-mini), Whisper, and Embeddings.

1. OpenAI API Official llms.txt & Clean Markdown Documentation

Official OpenAI Developer Portal

Feed this clean, token-efficient Markdown documentation directly to Antigravity, Cursor, or Claude Code to prevent hallucinations and outdated API syntax.

# Standard llms.txt Index Endpoint
https://developers.openai.com/llms.txt

# Comprehensive Documentation Bundle
https://developers.openai.com/llms-full.txt

Estimated Token Footprint: ~48k tokens (Fits smoothly inside standard 128k/1M context windows)

2. Production-Ready OpenAI API Cursor Rules (.cursorrules & .mdc)

OpenAI Python & TypeScript SDK guidelines, structured outputs, and streaming patterns. Save this into .cursor/rules/openai.mdc in your project repository.

// OpenAI SDK Rules
- Always use 'response_format: { type: "json_schema" }' for guaranteed structured outputs.
- Implement exponential backoff for 429 rate limit errors with jitter.
- For reasoning models (o1, o3-mini), do not pass custom temperature or system instructions (use developer messages).
- Stream responses for user-facing interactive chat with ReadableStream.

3. OpenAI API Antigravity & Claude Code System Instructions

Add this concise instruction block to your workspace .gemini/rules or project system prompt.

// Context Anchor for OpenAI API
When writing code for OpenAI API, refer directly to the verified specifications at https://developers.openai.com/llms.txt.
Follow strict error-handling and avoid deprecated API calls.

5. Troubleshooting: Common OpenAI API AI Coding Issues & Fixes

Frequently reported errors when LLMs generate OpenAI API code without proper context:

⚠️ Proactive Fix: Fix: Structured Outputs require `additionalProperties: false` on every object in the JSON schema.

6. Best Used With (OpenAI API Architecture Combos)

Engineers building with OpenAI API frequently combine these complementary developer frameworks: