OpenAI API Reference — Base URL, Auth & Endpoints
APIMaster.ai OpenAI-compatible API reference. Covers base URL, API key authentication (Bearer token), chat completions, image generation, and models endpoints for GPT-5.4, Claude, and DeepSeek.
API overview
Base URL
| Family | Base URL |
|---|---|
| OpenAI-compatible | https://apimaster.ai/v1 |
| Anthropic-compatible | https://apimaster.ai (no /v1) |
| Gemini (if enabled) | https://apimaster.ai (see console) |
Authentication
Authorization: Bearer <API_KEY>
Anthropic-style routes may accept x-api-key: <API_KEY> as well.
Main endpoints
| Method | Path | Description |
|---|---|---|
POST |
/chat/completions |
OpenAI Chat Completions |
GET |
/models |
Models available to your account |
POST |
/messages |
Anthropic Messages (when enabled) |
POST |
/images/generations |
Image generation (GPT-Image-2, etc.) — overview |
GET |
/tasks/{task_id} |
Poll async image tasks |
Use https://apimaster.ai/v1 for OpenAI SDK / Codex; use https://apimaster.ai as the Anthropic base URL (no /v1) for Claude Code and the Messages API.
Errors
JSON error bodies follow OpenAI/Anthropic conventions. Use HTTP status and error.message for retries.
Rate limits
Start with modest concurrency. On 429, use exponential backoff.
See Chat Completions and Models.