AGUI204

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

Message: Concatenated TOOL_CALL_ARGS for toolCallId '{toolCallId}' do not parse as JSON: {error}

Spec grounding

Frontends should concatenate these deltas in the order received to construct the complete arguments object.

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

Example

A violating stream from the corpus (spec/fixtures/invalid/AGUI204-args-not-json):

{"type":"RUN_STARTED","threadId":"thread_001","runId":"run_001","timestamp":1755300014000}
{"type":"TOOL_CALL_START","toolCallId":"call_001","toolCallName":"get_weather","timestamp":1755300014100}
{"type":"TOOL_CALL_ARGS","toolCallId":"call_001","delta":"{\"city\":","timestamp":1755300014200}
{"type":"TOOL_CALL_ARGS","toolCallId":"call_001","delta":"oops}","timestamp":1755300014300}
{"type":"TOOL_CALL_END","toolCallId":"call_001","timestamp":1755300014400}
{"type":"RUN_FINISHED","threadId":"thread_001","runId":"run_001","outcome":{"type":"success"},"timestamp":1755300014500}

Expected findings:

• error AGUI204 at event 4 — Concatenated TOOL_CALL_ARGS for toolCallId 'call_001' do not parse as JSON: Unexpected token 'o', "{"city":oops}" is not valid JSON