# X_MCP_ARGS_INVALID

## Means

tool arguments failed the input schema

## Typical cause

not raised on the wire since 22.10: invalid tool arguments answer an `isError` result carrying `X_INPUT_INVALID`; `McpArgsInvalidError` stays exported

## Fix

re-read `inputSchema` from `tools/list` and resend

[MCP and AI](/error-codes#mcp-and-ai)