X_MCP_TENANT_UNRESOLVED
Means
the tenant of an MCP call could not be resolved
Typical cause
defineAppMcp({ tenant: { resolve } }) threw, or answered an actor that is not an agent — a failed lookup is never read as "not a member"
Fix
defineAppMcp({ tenant: { arg, resolve: ({ person, value }) => (member ? agentActor({ id: person.id, orgId: value }) : null), list } }) — the cause names what refused; resolve answers a kind: 'agent' actor, or null for a non-member, and never throws