Human-readable API results (default or format=xmlfm, etc.) show a useful header api-format-prettyprint-header
The API help main page lists 90 API modules, one of which is query, and you can eventually find your submodule's help. Stephen Niedzielski commented "a nice improvement would be to link to the specific API used".
would link to the module help for pageimages at
(which ends up at https://en.wikipedia.org/w/api.php?action=help&modules=query%2Bpageimages)
It's a little tricky when the API request invokes multiple actions, multiple query submodules, generator, etc.. AIUI api.php can display help for multiple modules on one page but there's no TOC; it might be easier and better to provide multiple links:
The prettyprint header could also output a try in ApiSandbox link to load the query into ApiSandbox, similar to T89229: API Help should generate [try in ApiSandbox] link to Special:ApiSandbox#action=params from getExamples().