- This is Microsoft.
- He returns Webhook success with a code 200 and plaintext 1.
- He returns Webhook failure with a code 200 and a string tells its endpoint returned error 400.
- the string didn’t tell what exactly the error.
- Don’t be like Microsoft.
EDIT: Got a few details wrong since this happens a few months ago and this meme used to be on r/ProgrammerHumor. Also the proof: 
In this case I like to return a 502.
Great time to implement a 7XX code: https://github.com/joho/7XX-rfc
739 might be a good one
Nice! I’m definitely going to implement 787 at work.