[Bug] Runtime Error When Using File Search Tool in Azure AI Foundry Agents

[yashg-digi]

A runtime server_error occurs when using an Agent in Azure AI Foundry with the File Search tool enabled.
The agent functions normally without tools, but once File Search is added, any query immediately triggers a red error banner in the UI.
Network logs show the agentchatcompletions API returning "type": "server_error" with "message": "Unknown error".

The issue is agent-agnostic and reproducible across sessions.

Repro Steps

Steps to reproduce the behavior:

1. Go to Azure AI Foundry -> Agents.
2. Configure any agent and verify it works without tools.
3. Add File Search -> upload file and index.
4. Navigate to Playground.
5. Enter any prompt (e.g., “Test”, “What is the policy?”, etc.).
6. Observe the runtime error displayed in the UI and check the Network tab (agentchatcompletions) showing server_error.

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System Information

• OS: Windows
• Browser: Microsoft Edge
• Version: 142.0.3595.69 (Official build) (64-bit)

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Labels

• Feature Area: Tools -> File Search, Agents Playground
• Issue: Runtime Error, Server Error, Tool Invocation Failure

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Additional Context

• The error occurs consistently regardless of agent configuration.
• The error originates before any tool call is executed.
• This blocks all retrieval-augmented agent behavior.