External Requests

external name(arguments) using tool[fields] <- body. derives a request whose fields are known from the body. It does not execute the tool inside the engine.

world open.
socrates:Human.

external checkHuman(?Person) using _query[query -> "?- socrates:Human."]
    <- ?Person:Human.

?- `checkHuman(socrates)`[tool#requested -> true].

The query is true: the request exists. The tool has not yet run. Its object also has tool#name -> "_query" and tool#arg1 -> socrates. The # is a namespace separator, and backticks identify the request object.

Run a host to perform the request and write a receipt. Rules can then read tool#completed, tool#status, result("key") and row(N, "key"). An external operation is performed at most once per request identity within an episode; unlike an ordinary derived conclusion, its occurrence cannot be undone by withdrawing a premise. New attempts need new identities.

Give rule subjects class conditions so they do not accidentally match the request objects that also carry input slots. Keep input field names distinct from derived receipt fields to avoid conflicting request values. See Tool Calling for the complete request/receipt loop, and the Tool Reference for available hosts.