STEPS TO REPRODUCE: 1. Run Kate 2. Create new (ctrl + N) 3. Write something in 4. Try to Tools->External Tools->Tools->JSON Full File Format OBSERVED RESULT: 'Malformed URL' error was displayed. EXPECTED RESULT: Json formatting was applied to editor contents.
I am unable to replicate this on Kate 23.04.1. Can you please try using a snap or flatpak version of Kate as 21.12.3 is quite old and this issue is quite possibly already fixed.
You need to change the tool configuration so that it can read from STDIN. This is fixed in a later version AFAIR. Pasting a screenshot of what the config should look like. Alternatively, consider upgrading to the latest Kate version which has a formatting plugin that does the job in a much better way.
Created attachment 159489 [details] json format full file stdin