docs: uniform README (flesh out Installation/Usage/API)

README.md

@@ -11,10 +11,66 @@
 [![Ruff](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/astral-sh/ruff/main/assets/badge/v2.json)](https://github.com/astral-sh/ruff)
 [![ty](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/astral-sh/ty/main/assets/badge/v0.json)](https://github.com/astral-sh/ty)
 
-Integration of [Modern-DI](https://github.com/modern-python/modern-di) to FastAPI
+[Modern-DI](https://github.com/modern-python/modern-di) integration for [FastAPI](https://fastapi.tiangolo.com).
 
 Usage example: [fastapi-sqlalchemy-template](https://github.com/modern-python/fastapi-sqlalchemy-template)
 
+## Installation
+
+```bash
+uv add modern-di-fastapi      # or: pip install modern-di-fastapi
+```
+
+## Usage
+
+`setup_di` registers the container and builds a per-request child container automatically; `FromDI` resolves a provider (or type) into a route parameter.
+
+```python
+import dataclasses
+
+import fastapi
+from modern_di import Container, Group, Scope, providers
+from modern_di_fastapi import FromDI, setup_di
+
+
+@dataclasses.dataclass(kw_only=True)
+class Settings:
+    debug: bool = True
+
+
+@dataclasses.dataclass(kw_only=True)
+class UserService:
+    settings: Settings  # auto-injected by type
+
+
+class Dependencies(Group):
+    settings = providers.Factory(scope=Scope.APP, creator=Settings)
+    user_service = providers.Factory(scope=Scope.REQUEST, creator=UserService)
+
+
+app = fastapi.FastAPI()
+container = Container(groups=[Dependencies], validate=True)
+setup_di(app, container)
+
+
+@app.get("/")
+async def index(user_service: UserService = FromDI(Dependencies.user_service)) -> dict[str, bool]:
+    return {"debug": user_service.settings.debug}
+```
+
+The framework `Request` / `WebSocket` are resolvable within DI via the pre-built `fastapi_request_provider` / `fastapi_websocket_provider` context providers.
+
+## API
+
+| Symbol | Description |
+|---|---|
+| `setup_di(app, container)` | Stores the container on `app.state` and appends a lifespan that closes it on shutdown (merges with any existing `lifespan=`) |
+| `FromDI(provider, *, use_cache=True)` | FastAPI `Depends` that resolves a provider (or type) from the per-request child container |
+| `fetch_di_container(app)` | Returns the app-scoped container from `app.state` |
+| `build_di_container(connection)` | FastAPI `Depends` callable that yields the per-request child container — `REQUEST` scope for an HTTP request, `SESSION` scope for a WebSocket |
+| `fastapi_request_provider` | `ContextProvider` for the current `fastapi.Request` |
+| `fastapi_websocket_provider` | `ContextProvider` for the current `fastapi.WebSocket` |
+
 ## 📦 [PyPI](https://pypi.org/project/modern-di-fastapi)
 
 ## 📝 [License](LICENSE)