MCP Tool Parameter Handling - JSON Object Validation Issue

[Marcus_Kim]

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

I’m encountering parameter validation issues when using MCP tools in Cursor IDE, specifically with the Notion integration. The tool appears to be incorrectly validating JSON object parameters as strings.
Error Details:
Tool: mcp_Notion_notion-update-page
Error: “MCP error -32602: Invalid arguments”
Validation Issue: “Expected object, received string” for data parameter
Problem: Tool schema validation rejecting properly formatted JSON objects

{ "data": { "page_id": "300f41f9-113d-4e7e-9300-345582d04ecb", "properties": { "Status": { "status": { "name": "In Progress" } } } } }

Steps to Reproduce

Ask Cursor to update a Notion database

Expected Behavior

Expected Behavior:
The MCP tool should accept the data parameter as a JSON object without string validation errors.

Screenshots / Screen Recordings

Operating System

MacOS

Current Cursor Version (Menu → About Cursor → Copy)

Version: 1.5.9 (Universal)
VSCode Version: 1.99.3
Commit: de327274300c6f38ec9f4240d11e82c3b0660b20
Date: 2025-08-30T21:02:27.236Z
Electron: 34.5.8
Chromium: 132.0.6834.210
Node.js: 20.19.1
V8: 13.2.152.41-electron.0
OS: Darwin x64 24.5.0

Does this stop you from using Cursor

No - Cursor works, but with this issue

[condor (Condor (Tee))]

hi @Marcus_Kim and thank you for the detailed bug report.

Could you share which model you are using and also post a Request ID with privacy disabled so we can look into the details? Cursor – Getting a Request ID