One of resources in my RESTfull web-service, which performs a search operation, has a lot of criteria/parameters.

In the current implementation this search criteria is passed like a dictionary with option mnemonics as keys. E.g.

```
{'fieldl_greater_equal' : <value>,
 'field2_like' : <value>,
  ...}

```

The questions are:

What is the best way to introduce list of allowed mnemonics and allowed values for each mnemonic (i.e. interface of the system) to my clients?

Should I move those mnemonics to inurl-parameters?

How to make such resource easy-extendable?

Any suggestions and receipts of how such system should be implemented?

Web-service is implementing on Python.