When this category is the right fit
Developer tools are best when you are dealing with structured data, encoded strings, timestamps, SQL, regular expressions, or temporary test data. The value is speed: you can paste something from a log, API response, email, or config file and get a useful answer without opening a full project or installing another extension.
These tools work especially well for short debugging loops. You can verify whether a payload is valid JSON, inspect an encoded parameter, test a regex, or convert an XML fragment before sending it back to another system.