Questions about the built-in API **HELP PAGES** at api.stackexchange.com/docs. For issues with the API itself, use the [api] tag, not this tag.
Stack Exchange provides extensive documentation for the API which can be found at api.stackexchange.com/docs.
The doc pages also have handy "Try It" tools that let you preview live API calls and tweak filters for almost all methods.
Use this tag (api-help) if you have an issue with one or more of these doc pages.
But, more likely your issue is with the API itself. Use the api tag for that.