422
providers.invalid_routeprovidersRule R13The route is not valid
SetRoute refuses a provider code that is not registered, does not support the method, or is disabled — before storing anything. An empty list for a tenant removes that tenant's override rather than storing "no providers".
Why the API refuses
WHEN SetRoute is executed, THE SYSTEM SHALL reject a provider code that is not registered, does not support the method or is disabled; otherwise it SHALL store the ordered list with the caller's reason, bump the route version and emit RouteChanged, and an empty list for a tenant SHALL remove that tenant's override.
What to do
Register and enable the provider, and check it supports the method, before putting it in a route. The refusal is per-entry; detail names which one.