Every API error looks different right now

Half my endpoints raise HTTPException. The other half just return a raw dict, and nothing matches.

Beginner to intermediateRead 5 minDoing: an hour, with your project open7 steps

▶ Start

What you'll have at the end

The same error fields returned on every failed request, whatever the cause

Before you start

You need

An app with at least one route raising an HTTPException for its errors, at least one route whose request body is checked by a model, and at least one other route that returns a plain dict or JSON response by hand instead of raising anything.

Not covered

Choosing which status code fits a given failure, 400 versus 422 versus 409. This assumes you already know the code you want and only fixes the shape wrapped around it.

Leans on

Design the one shape every failure will share

Pick the fields every failure will share
Write one function that builds that shape

Wire every error the app already raises through it

Catch the errors you already raise on purpose
Fold the automatic validation error in too
Catch the bug nobody planned for

Close the gap and prove it

Replace a raw return with a raise
Trigger three failures and compare

Where to go next

Validate a request body with a Pydantic model

for building the model and its field rules in the first place. This recipe assumes that model already exists and only reshapes the failure it produces.

No shared ID across the log lines for one request

for turning the catch-all handler's bare log line into one you can trace back to the request that caused it.

Checked 18 Aug 2026

Part of the FastAPI cookbook