Multi-Tenant MCP: Isolation Patterns That Hold Up

Every multi-tenant MCP deployment starts with the same instinct: put a tenant_id in the JWT, scope every tool call to it, and call the isolation problem solved. It isn't. The gap between "scoped by claim" and "actually isolated" is exactly where these deployments fail in production — not in testing, where a single code path is exercised, but in production, where a new tool handler forgets the…