How Do I Send a CURL POST Request with Headers and JSON Data? or What’s the Correct Syntax for a CURL

400 usually means the server didn’t like your request. Could be:
- Missing/incorrect headers (you got Content-Type, but maybe it needs Auth?)
- Malformed JSON (even a tiny typo breaks it)
- Server expecting something else (like form-data instead of JSON)

Try this tool: https://reqbin.com/ to test your payload separately. Helps narrow it down!