It would be useful if we added a GetAgentFeatures() gRPC call:

message AgentFeaturesResponse {
    bool supports_seccomp = 1;
};

rpc GetAgentFeatures(AgentFeaturesRequest) returns (AgentFeaturesResponse);

This call could be used by the runtime to determine the capabilities of the agent. For seccomp, that would allow the runtime to either send the seccomp profile (if the agent supports it), or potentially to remove the seccomp profile if it doesn't.

Along with showing whether the agent was built with seccomp support, we could also add the same details to AgentFeaturesResponse that are displayed by the announce() call.

Alternative: if we want to minimise new calls, we do already have GetGuestDetails(), so that could be extended to also return agent details.

Related: kata-containers/runtime#689