# X_MCP_TENANT_INVALID

## Means

defineAppMcp declares its tenant argument inconsistently

## Typical cause

tenant.arg is not a plain argument name, or a tool of this server already declares an input property of that name

## Fix

`defineAppMcp({ tenant: { arg: 'tenant', resolve, list } }) — pick an argument name no tool's input declares`

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