invalid_header_tool

MCP tool from Inspector by modelcontextprotocol

an annotation using the header name "Bad Header". The space makes it an invalid RFC 9110 token, so the whole tool definition is invalid.

How to use it

Project documentation lists invalid_header_tool for the Inspector MCP server. Add the server to your MCP client (Claude Desktop, Cursor, Windsurf and others), then check which tools your installed version makes available. Tool availability can depend on configuration and credentials. A server handshake does not verify this tool’s behavior. See the full listing for setup details.

Install Inspector

$npx @modelcontextprotocol/inspector # web UI (default)

FULL INSPECTOR LISTING

Other tools in Inspector (3)

echo

plain tool.

get_weather

a valid x-mcp-header: "City" annotation on its city argument.

trigger_invalid_params

answered with a real -32602 Invalid params error whose message is not about a missing tool.