[BUG] MCP server returns no tools with invalid_literal error

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?

I configured Claude Desktop with an MCP server using the claude mcp serve command as described in the docs. When I attempt to load tools, Claude Code reports that no tools are returned. As a result, Claude Code in Claude Desktop shows an empty list of tools instead of commands like View, Edit, and LS.

What Should Happen?

I'm not exactly sure because there's not too much good documentation on how or what tools Claude should expose as an MCP server, but not exposing any tools definitely isn't the expected scenario.

Error Messages/Logs

The MCP inspector UI displays the following errors:\n\n
[
  {
    "code": "invalid_literal",
    "expected": "object",
    "path": ["tools", 0, "outputSchema", "type"],
    "message": "Invalid literal value, expected \"object\""
  },
  {
    "code": "invalid_literal",
    "expected": "object",
    "path": ["tools", 5, "outputSchema", "type"],
    "message": "Invalid literal value, expected \"object\""
  }
]

Steps to Reproduce

1. Add the mcpServers configuration to claude_desktop_config.json pointing to the claude mcp serve command.
2. Launch Claude Desktop.
3. Ask Claude to list available tools or run a command (e.g., ask Claude to view a file or list a directory).
4. Observe that Claude Desktop reports no available tools.
5. Open the MCP inspector UI and see the invalid_literal errors shown above.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.0.30 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Non-interactive/CI environment

Additional Information

_No response_