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

400 Bad Request usually means the server’s picky about something. Try these:
1. Escape special chars in your JSON (like quotes).
2. Use `--data-raw` instead of `-d` if your shell’s messing with the data.
3. Check if the endpoint requires a trailing slash (weird, but happens).

For debugging, `curl -v` is overwhelming, but grep for "HTTP/" to skip the noise.