Should this Json result return a 404 or 200?

Question

I'm trying to make an API sorta loosly based on StackExchange's api results.

So here's my json output.

{
    "items" : [ ... objects in here .... ]
    "page" : 
    "page_size" :  
    "total_pages" : 
    "total_items_count" :  
    "maximum_quota" : 
    "remaining_quota" : 
}

pretty damn simple.

Now, I'm not sure what do to if the person tries to request a .. um .. product or question or whatever, and the item doesn't exist.

eg..

{
    "items": []
    ... snipped ....
}

I was thinking I would return a 200 AND the Json above, with the Items property being empty.

The other idea I had was returning that json with the items property empty BUT setting the response http status to 404.

Thoughts / standards ?

I really want to return the json no matter what. Why? the quota's. Even an empty result is still a legit hit to the api service.

Answer 1

In my opinion I would return a 400 & 204 status:

http://en.wikipedia.org/wiki/List_of_HTTP_status_codes

400 Bad Request

The request cannot be fulfilled due to bad syntax.[2]

If you pass an invalid argument, a 400 status is returned saying the request is bad.

In this scenario, I wouldn't return any JSON message back. It's invalid, sort it out. The StatusMessage can say 'Invalid Argument', but no content.

---

204 No Content

The server successfully processed the request, but is not returning any content.[2]

If you pass valid arguments, but the content wasn't found, you can say it wasn't found.

You may* want to pass some additional info back, may not.

For Twitter, say you wanted to search for '@JohnDoe' user, and it wasn't found. You could say 204, with: "Sorry we couldn't find @JohnDoe, but we did find these 3 similar people that may be what you want" in which case you wouldn't push down their details, just the Twitter names.

However if you were searching for a tweet, and it wasn't found, there's no reason to send any additional info to the client. Just say it wasn't found, end of story.