Endpoint

An API is the whole window. An endpoint is one labeled slot on it.

GET /todos is an endpoint. POST /todos is another, even if the path looks the same. The HTTP method is part of the label. You do not talk to "the API" in the abstract. You pick one slot and you ask for that job.

Path plus verb

In the app the builder scaffolds, those slots are URLs your frontend already knows:

• /api/todos — list or create
• /api/todos/12 — one row
• /api/auth/callback — the auth handshake

A 404 means that slot is not on today's menu. Check the spelling and the verb before you rewrite the kitchen. A 401 means the slot exists and you did not bring a key.

Your agent does not talk to "the backend" as a blob either. It walks the list. Fetch the todos. Create one. Mark it done. Three slots. Three trips.

Name them like a stranger would

REST wants nouns in the path. Keep the verbs in the method. /deleteTodo is a slot you will hate at 4 a.m. /todos/12 plus DELETE is a slot another tool can guess.

When something fails on stage, the error is usually "wrong slot," not "the internet is down." Read the path. Read the method. Then change code. A webhook is just another slot that strangers POST into — public, picky, and easy to misspell in the vendor dashboard.

What this unlocks

Once you see slots, debugging stops being mystical.

The 404 is a missing label. The 200 is the slot you meant. Pick the slot, then argue about the body.