REST API Framework. Recommended behavior for invalid querystring parameter

Question

I am implementing a REST API Framework, and I wonder what the recommendedbehavior is, when a client submits an invalid querystring parameter.

I will illustrate what

Answer 1

Following the letter of the law, the response should be a 404 Not found. However, nobody is going to get too upset with you if you prefer to return 400 - bad request.

I would definitely return a 4XX status code though. You want the client to know that they made an error.