fix: add validation and warnings for large MCP tool arguments

[roomote]

Fixes #6108

Problem

MCP tool calls were being truncated around 4000 characters when passing large JSON arguments. This was happening because some language models have internal limits on the size of tool call arguments they can generate.

Solution

Added validation in the MCP tool handler to:

1. Detect when arguments appear to be truncated (invalid JSON ending around 4000 chars)
2. Show helpful error messages explaining the truncation and suggesting smaller data chunks
3. Warn users when arguments are large but still valid JSON (over 3800 chars)

Changes

• Modified useMcpToolTool.ts to add truncation detection and validation
• Added comprehensive tests for the new validation logic
• Error messages guide users to break operations into smaller chunks

Testing

• Added 4 new test cases covering:
  • Large but valid JSON arguments (warning case)
  • Truncated JSON arguments (error case)
  • JSON ending with incomplete array (truncation detection)
  • Normal invalid JSON (existing behavior preserved)
• All existing tests continue to pass

This provides a better user experience by clearly explaining when and why MCP tool calls fail due to size limitations.

---

Important

Adds validation and warnings for large MCP tool arguments in useMcpToolTool.ts, improving error handling for truncated JSON.

• Behavior:
  • Adds validation in useMcpToolTool.ts to detect truncated JSON arguments and warn users for large but valid JSON (over 3800 chars).
  • Provides error messages for truncated JSON, suggesting smaller data chunks.
• Testing:
  • Adds 4 new test cases in useMcpToolTool.spec.ts for large JSON warnings, truncated JSON errors, incomplete array detection, and normal invalid JSON.
  • Ensures all existing tests pass.
• Misc:
  • Error messages guide users to break operations into smaller chunks.

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[daniel-lxs]

The issue doesn't have enough information to propose a fix yet, closing