userFunctionResponse
fun userFunctionResponse(name: String, id: String?, response: Map<String, Any?> = emptyMap()): Content
A user-role Content carrying a single FunctionResponse - what the caller sends back when resuming after a long-running tool, an HITL approval, or a manual function-response injection.
id has no default: a resume lookup matches on it, so a test that means to omit it has to write id = null rather than leaving it off by accident.