```python
from fastapi import FastAPI, Request, Response

import helpers  # noqa: F401  (the provided API)

app = FastAPI()


@app.post("/thumbnail")
async def thumbnail(request: Request):
    data = await request.body()
    thumbnail_bytes = helpers.resize_image(data)
    return Response(
        content=f'{{"size": {len(thumbnail_bytes)}}}'.encode("utf-8"),
        media_type="application/json",
        status_code=200,
    )
```