400 errors are the worst! When I was struggling with curl sending JSON, I realized the API expected the JSON to be in a specific format. Try this:
```bash
curl -X POST -H "Content-Type: application/json" -d '{"key": "value", "another_key": "another_value"}' https://example.com/api
```
Also, make sure your JSON keys and values are wrapped in double quotes, not single quotes. Some APIs are super strict about that.
```bash
curl -X POST -H "Content-Type: application/json" -d '{"key": "value", "another_key": "another_value"}' https://example.com/api
```
Also, make sure your JSON keys and values are wrapped in double quotes, not single quotes. Some APIs are super strict about that.