# §7 — Who is calling it?

An API that knows who is calling is a different program from one that does not — different tables, different failure modes, a different amount of your life spent on it.

Answer for the callers you have on the first day. Adding accounts later is a migration. Building accounts you do not need yet is a month.

## Where now

- Anyone. It is public. — turn to §53
- People, with accounts — turn to §12
- Other machines, with tokens you issue — turn to §77 (You are becoming the identity provider.)
- An agent, on someone's behalf — turn to §41