[BUG] Claude Code cannot handle an MCP tool param that is an empty string

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Here's the repo that reproduces the bug: https://github.com/LegalRabbit-AI/claude-code-mcp-empty-string-bug

If an MCP tool call has a param whose value is empty string, then Claude Code will invoke the tool with no param.

What Should Happen?

It should invoke the tool with the correct params.

Error Messages/Logs

Steps to Reproduce

Here's the repo that reproduces the bug: https://github.com/LegalRabbit-AI/claude-code-mcp-empty-string-bug

You'll need to run a toy MCP server.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.150

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_