How do I format and validate JSON when an API returns an error?

Half the "broken JSON" cases are truncated responses, not malformed data. Quick workflow:

1. Paste the raw response into a validator – the JSON Formatter on tools.php shows the error line instantly
2. Check for truncation – a missing closing brace at the end usually means the response was cut off, not invalid
3. Validate against a schema – in Python:

Code:

import jsonschema
jsonschema.validate(data, schema)

4. Log the raw body before parsing – debugging blind is where time goes to die

When an API "returns an error", the first question is always: valid JSON, or truncated?

What's your #1 cause of JSON errors?