Format the response first
Say the API returns {"code":0,"data":{"userId":1001,"token":"eyJ..."}}. You can’t read that. Paste it into JSON Formatter; the tree opens and syntax lights up.
If parse fails, the error usually sits near a line number. Trailing commas and HTML error pages pretending to be JSON are the usual culprits. Check Content-Type before you blame your own code.
Decode the JWT and read exp
Copy the token (drop the Bearer prefix) into JWT Decoder. Look at exp, iss, and whatever custom claims you care about.
Example: "exp": 1718123456. Timestamp Converter in seconds mode turns that into a date you can read. Expired token + 401? You already know why.
Diff old vs new payloads
Before a release, paste yesterday’s sample and today’s into JSON Diff. New keys, deleted fields, userId number→string — easier than squinting at a changelog, especially when mobile and web share one API.
Save the path if you repeat it
JSON Formatter → JWT Decoder → Timestamp Converter makes a fine pipeline for the weekly grind. The Chrome extension can open the right tool from selected text with ?input= filled in.
Dev tools here run in the browser. Fine for staging. Don’t paste production secrets.