I've written probably half a dozen unrelated apps that call REST APIs and I think they all implemented REST differently. Some treat PUT as insert while POST as update. Some treat POST as insert, PUT as insert/update. Some return 201 when insert was successful, some return 200 whenever anything is successful. Some issue tokens, some authenticate using headers.

Just last night I wrote some code to auto-create Trello cards and assign them to a specific list. The https://trello.com/docs/ seem fairly decent but what they don't tell you is that POST is insert, PUT is update. Moreover, while you can assign a due date via PUT ( https://trello.com/docs/api/card/index.html#put-1-cards-card... ), you cannot assign one via POST ( https://trello.com/docs/api/card/index.html#post-1-cards ). So if you want to create a card with a due date, you have to POST, read ID, then PUT the due date to /card/id.

The problem with people trying to be RESTful is that they pay too much attention to stuff that doesn't matter (71 status codes) instead of stuff that really matters (simplify complex insert/update). I'd rather have Trello return 400 on errors and provide a text description than use one of the 30+ 4xx errors. And I'd rather have them accept due date when inserting a card. Trying to conform to REST's standards is like trying to be XHTML compliant. Great, your site validates. But you're still using white font on yellow background!

Be as RESTful as you need to be. But more than that, be useful and sensible. Don't make me call your server six times to make one valid GET request.