AGUI201

Severity: error · Group: Tool calls · Checked in: core · Since: 0.x

Message: TOOL_CALL_ARGS for toolCallId '{toolCallId}' with no open TOOL_CALL_START

Spec grounding

When an agent needs to use a tool, it emits a ToolCallStart event, followed by one or more ToolCallArgs events that stream the arguments being passed to the tool, and concludes with a ToolCallEnd event.

Source: https://docs.ag-ui.com/concepts/events#tool-call-events

Example

A violating stream from the corpus (spec/fixtures/invalid/AGUI201-args-without-start):

{"type":"RUN_STARTED","threadId":"thread_001","runId":"run_001","timestamp":1755300013000}
{"type":"TOOL_CALL_ARGS","toolCallId":"call_ghost","delta":"{}","timestamp":1755300013100}
{"type":"RUN_FINISHED","threadId":"thread_001","runId":"run_001","outcome":{"type":"success"},"timestamp":1755300013200}

Expected findings:

• error AGUI201 at event 1 — TOOL_CALL_ARGS for toolCallId 'call_ghost' with no open TOOL_CALL_START