Turn a dense API doc into a working mental model in an hour

You are teaching me an unfamiliar API I have to build against today. Below is its documentation. Do not summarise it - build me a mental model.

Give me:

1. THE SHAPE — the 5-8 core objects and how they relate, written as plain sentences ("an X belongs to a Y and can have many Z").
2. THE HAPPY PATH — the exact sequence of calls for the most common real task, one line each, with what you get back.
3. WHERE PEOPLE GET STUCK — 4 things the docs mention once that will cost me an afternoon (auth scopes, pagination, rate limits, async jobs, id formats).
4. VOCABULARY — terms this API uses differently from how the rest of the world uses them.
5. FIRST EXERCISE — one small task I should build to prove I understand it, plus how I will know I got it right.

Rules: no preamble, no marketing language from the docs. If the documentation does not cover something, say "not documented" rather than filling it in from a similar API.

DOCUMENTATION:
{{paste the reference pages, or the endpoint list plus one full example request and response}}

WHAT I NEED TO BUILD:
{{one sentence}}