# API: Endpoint Coverage
### Scope
- **Purpose**: Define required OpenAI API endpoint coverage and the feature-gating policy for all optional capabilities in `api_openai`.
- **Responsibility**: Crate maintainers; every listed core endpoint must be implemented — a missing endpoint is a missing feature.
- **In Scope**: All client methods and optional feature modules wrapping API endpoints.
- **Out of Scope**: Provider-specific extensions not in OpenAI's published API surface.
### Abstract
The `api_openai` crate provides a thin HTTP client covering OpenAI API endpoints. Each method maps one-to-one to an OpenAI API path. Optional capabilities are independently gated by Cargo feature flags and require explicit opt-in. The crate is the largest in the `api_llm` workspace (108 source files) and covers the full OpenAI API surface.
### Operations
| Chat completions (`/v1/chat/completions`) | always-on | Primary conversational AI interface |
| Streaming chat | `streaming` | SSE via eventsource-stream |
| Responses API | always-on | Create, retrieve, update, cancel, delete |
| Embeddings (`/v1/embeddings`) | always-on | Text-to-vector conversion |
| Models (`/v1/models`) | always-on | Model listing and retrieval |
| Images (`/v1/images`) | always-on | Generation, editing, variations |
| Audio (`/v1/audio`) | always-on | Speech-to-text and text-to-speech |
| Files (`/v1/files`) | always-on | File upload and management |
| Fine-tuning (`/v1/fine_tuning`) | always-on | Model fine-tuning operations |
| Moderations (`/v1/moderations`) | always-on | Content moderation |
| Assistants (`/v1/assistants`) | always-on | Assistant lifecycle management |
| Realtime WebSocket | `websocket` | Bidirectional real-time API |
Feature-gating policy: `enabled` is the master switch. `full` activates all features. `integration` enables integration test compilation. `default = ["full"]` for ease of use.
### Error Handling
All API methods return `Result<T, error_tools::Error>`. Error variants cover authentication failures (401), rate limits (429), server errors (5xx), network timeouts, and serialization failures. The `error_tools` crate is the exclusive error infrastructure.
### Sources
| `src/lib.rs` | Top-level module declarations — all endpoint modules registered here |
| `src/components/` | Shared request/response types for all API endpoints |
| `src/realtime/` | WebSocket realtime endpoint (gated on `websocket` feature) |
### Tests
| `tests/` | Integration tests covering all major endpoint groups against real OpenAI API |