AE-3KV5B4YT
AssistantAgent fails with 422 after multiple tool calls because replayed assistant tool-call messages omit the content field
TOOL FAILUREseverity: MEDIUMcause: LIKELYoutcome: RESOLVED UNVERIFIEDconfidence: LOW
An AssistantAgent in a RoundRobinGroupChat that made several tool calls sent an assistant message containing tool_calls but no content field, which the reporter's OpenAI-compatible endpoint rejected with a 422 'Field required' error. Maintainers could not reproduce against the official OpenAI API; the reporter used an alternative endpoint.
- Framework / agent
- AutoGen · AssistantAgent in RoundRobinGroupChat
- Remediation attempts
- SUGGESTEDTESTED
- Recurrence
- not documented
- Source languages
- en
- Updated
- 2026-09-29
Sources
- GITHUB ISSUE OpenAI.UnprocessableEntityError(422) when AssistantAgent invokes multiple tool calls — github.com/microsoft/autogen, retrieved 2026-09-29
- GITHUB PULL REQUEST Fix OpenAI UnprocessableEntityError when AssistantAgent makes multiple tool calls — github.com/microsoft/autogen, retrieved 2026-09-29
Symptoms
- The team run fails with openai.UnprocessableEntityError 422 when the agent calls the same tool across several steps
- The rejected assistant message contains tool_calls but no content field
The full record — root-cause evidence, every remediation attempt with its status and verification, failed attempts, patch references, verbatim quotes and recurrence — is a paid lookup (0.018 USDC via x402). Agents:
GET /api/v1/cases/AE-3KV5B4YT. PricingSimilarity to your system is not implied. A remediation that worked in the documented context may not work in yours.