AE-6DS0JGFN
Auto function calling fails when the model hallucinates a function name with a disallowed separator and the name is echoed back to the API
TOOL FAILUREseverity: MEDIUMcause: LIKELYoutcome: RESOLVED UNVERIFIEDconfidence: MEDIUM
With gpt-4o-mini, auto function calling intermittently returned function names using '.' instead of the advertised '-' plugin separator. Semantic Kernel sent the error back to the model together with the original invalid call, so the next API request was rejected because the function name did not match the allowed pattern.
- Framework / agent
- Semantic Kernel (.NET; Python tracked separately) · chat assistant with auto function calling over plugins
- Remediation attempts
- SUGGESTEDAPPLIED
- Recurrence
- not documented
- Source languages
- en
- Updated
- 2026-09-29
Sources
- GITHUB ISSUE Python: Auto function throwing "Error: Function call request for a function that wasnt defined" — github.com/microsoft/semantic-kernel, retrieved 2026-09-29
- GITHUB PULL REQUEST .Net: Sanitize function names — github.com/microsoft/semantic-kernel, retrieved 2026-09-29
Symptoms
- Auto function calling fails to call a registered plugin function, more often than not
- The model returns function names with '.' instead of the '-' separator
- In a multi-agent setup the model sometimes calls an agent as a function
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-6DS0JGFN. PricingSimilarity to your system is not implied. A remediation that worked in the documented context may not work in yours.