What format is used for communication between clients and servers using MCP messages?	JSON
What is the relationship between a "Request" message type and its corresponding "Result" message type?	They are always paired; the result is the expected response to the request.
What type of message is used to signal an event that occurs but does not require a response?	Notification message
What is the primary purpose of the `call tool request` message?	To instruct the MCP server to run a specified tool.
Where is the comprehensive list of all available MCP message types defined?	In the `schema.ts` file within the MCP specification repository.
What category of messages describes all types of requests expected to be sent *from* the client?	Client Request
What is the critical takeaway regarding message directionality for the streamable HTTP transport?	Understanding messages sent from the server over to the client (Server Requests and Server Notifications).