# fastapi.exceptions.FastAPIError: Invalid args for response field

- **ID:** `python/fastapi-multiple-body-parameters`
- **Domain:** python
- **Category:** type_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

Using multiple body parameters without embedding them in a single Pydantic model.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.x | active | — | — |

## Workarounds

1. **** (95% success)
   ```
   class Item(BaseModel):
    name: str
    price: float

@app.post('/item')
async def create(item: Item):
    return item
   ```
2. **** (85% success)
   ```
   Use Body(embed=True) for a single param: async def create(item: str = Body(embed=True))
   ```

## Dead Ends

- **** — FastAPI expects a single body; multiple params cause confusion. (90% fail)
- **** — Loses validation and type safety. (70% fail)