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Error: "Invalid 'tools': array too long" when using Copilot GPT 5.1 #4909
Description
Description
- Issue: When using Copilot GPT 5.1, an error occurs:
Invalid 'tools': array too long. Expected an array with maximum length 128, but got an array with length 142 instead.
-
Expected Behavior:
The system should handle arrays up to the documented maximum length or provide clear guidance to limit array size. -
Actual Behavior:
The error is thrown and the workflow fails. -
Impact:
Blocks usage of Copilot GPT 5.1.
OpenCode version
1.0.120
Steps to reproduce
- Use Copilot GPT 5.1 in OpenCode.
- Execute any workflow that initializes the
toolsarray exceeding 128 entries.
Screenshot and/or share link
Operating System
Pop!_OS 22.04 LTS
Terminal
Ghostty
Activity
github-actions commentedon Nov 29, 2025
This issue might be a duplicate of existing issues. Please check:
This is a known limitation where GitHub Copilot models have a maximum of 128 tools, and exceeding this limit causes the 'Invalid tools: array too long' error you're experiencing. The referenced issue proposes implementing a virtual tools concept to automatically activate tools on demand, similar to VSCode's implementation.
Feel free to ignore if none of these address your specific case.
rekram1-node commentedon Nov 29, 2025
You have one or more mcp servers with a lottt of tools
rekram1-node commentedon Nov 29, 2025
This many tools will degrade llm performance and completely eat up your already limited context window on github copilot
itse4elhaam commentedon Nov 29, 2025
Yeah, I was already thinking of it, think this is my sign to fix it 😅