フリー問題

問題文

A server receives a request whose _meta lacks the required clientCapabilities field. What must it do?

選択肢

1. Fall back to the capabilities the same client declared on an earlier request over the same connection, since that is the least disruptive behavior and the connection identity is available to the server at that point in the exchange.
2. Reject the request with -32602, and on HTTP respond with 400 Bad Request.
3. Assume an empty capabilities object and proceed, since the field is only a hint about optional behavior.
4. Return -32021 with the list of missing capabilities, which the client fills in and then resends.