MacOS Copilot Visual Studio Code Agent Mode - sequencialthinking

Describe the bug
Every command that triggers sequencialthinking mcp is returning error.

To Reproduce
Steps to reproduce the behavior:

Copilot in Agent mode do any query with #sequentialthinking eg. #sequentialthinking how to create a new react project?

Expected behavior
Think, create a plan and then print out instructions about how to create a new react project.

Logs

GitHub Copilot
2025-05-13 15:53:38.039 [warning] Tool bb7_sequentialthinking failed validation: object has unsupported schema keyword 'minimum'
2025-05-13 15:53:38.039 [warning] Tool bb7_sequentialthinking failed validation: object has unsupported schema keyword 'minimum'
2025-05-13 15:53:38.039 [warning] Tool bb7_sequentialthinking failed validation: object has unsupported schema keyword 'minimum'
2025-05-13 15:53:38.039 [warning] Tool bb7_sequentialthinking failed validation: object has unsupported schema keyword 'minimum'
2025-05-13 15:53:38.447 [info] Request ID for failed request: 93b7029a-bd34-462b-81b4-29b0ac6dac45
2025-05-13 15:53:38.448 [error] Request Failed: 400 Bad Request
2025-05-13 15:53:38.451 [error] Error: Failed to compute args for tool: "bb7_sequentialthinking" (at tsx element Ok > YM > mde > jSe > tS > Cre > rr)

Additional context
This is probably not an issue with the MCP itself since it wasn't changed in a while, but likely something changed with copilot which might require changes in the MCP?

what is sequentialthinking context ? it's your instructions file ?

I have the same issue on Windows. Nothing else in context. Noticed that problem started after updating VS Code to v1.100, and persists in v1.100.1.

Version: 1.100.1 (user setup)
Commit: 91fa95bccb027ece6a968589bb1d662fa9c8e170
Date: 2025-05-09T15:43:50.040Z
Electron: 34.5.1
ElectronBuildId: 11369351
Chromium: 132.0.6834.210
Node.js: 20.19.0
V8: 13.2.152.41-electron.0
OS: Windows_NT x64 10.0.26100

what is sequentialthinking context ? it's your instructions file ?

I use #sequentialthinking to trigger copilot agent to use the sequentialthinking MCP

Having same issue after vs code update, think something changed in new one.

Having the same issue.

I just updated to VS Code v1.100.2 and this specific issue seems to have been resolved.

Failed to compute args for tool: "f1e_sequentialthinking" (at tsx element Ok > YM > mde > jSe > tS > Cre > rr)

UPDATE: I take that back. It works/fails intermittently, but can't explain why and under what circumstances yet.

Hey! I ran into a similar pattern in our bug knowledge base and thought this might help.

What's happening: VS Code v1.100+ Copilot Agent Mode started strictly validating MCP tool JSON schemas and rejects keywords like minimum/maximum. The sequentialthinking tool schema uses minimum: 1 on properties like totalThoughts and nextThoughtNeeded, which fails this stricter validation.

What worked for us:

Remove minimum, maximum, and any other JSON Schema keywords not in the subset supported by VS Code Copilot (which only allows basic type, description, properties, required, enum, items, additionalProperties). In the @modelcontextprotocol/server-sequential-thinking package, strip minimum from the totalThoughts and thoughtNumber property definitions in the tool schema. Alternatively, downgrade VS Code to <1.100 as a workaround.

// In src/index.ts of @modelcontextprotocol/server-sequential-thinking
// Remove `minimum` from these property definitions:

// Before:
//   thoughtNumber: { type: 'integer', description: '...', minimum: 1 },
//   totalThoughts: { type: 'integer', description: '...', minimum: 1 },

// After:
//   thoughtNumber: { type: 'integer', description: '...' },
//   totalThoughts: { type: 'integer', description: '...' },

Hope this helps! Let me know if it doesn't match your case — happy to dig deeper. 🦞

Disclosure: This analysis is from Confucius Debug, an AI-powered community KB for agent bugs. Please verify before applying.

_{🦞 Confucius Debug — community knowledge base for AI agent bugs. Free to search via MCP.}

Closing: superseded by the v2 release.

Thank you for reporting this, and apologies for the long wait for a response.

Since this was filed, the reference servers have been rebuilt for the 2026-07-28 MCP specification (#4857) and released as v2 (2.0.0 on npm for the TypeScript servers, 2026.10.19 on PyPI for the Python servers). Each server now runs on v2 of its SDK, and the behavior described here has either been fixed or no longer exists in the same form. 'minimum' is a standard JSON Schema keyword; the rejection came from a VS Code Copilot validation change at the time, not a defect in the sequential-thinking server.

This is not a judgment on whether the problem was real; it's a consequence of the code it describes having been replaced. This is happening as part of the backlog triage in #4875.

If this still happens on the v2 release, we'd genuinely like to know. Please open a fresh issue with the version you're running and steps to reproduce, and we'll look at it. Note that this repository accepts contributions as issues rather than pull requests; see CONTRIBUTING.md.

Thanks for taking the time to report it.

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MacOS Copilot Visual Studio Code Agent Mode - sequencialthinking #1752

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MacOS Copilot Visual Studio Code Agent Mode - sequencialthinking #1752

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ennbou commented on May 13, 2025

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