What are the main request-result message pairs in MCP?

The main request-result pairs include Call Tool Request and Call Tool Result for executing server tools, List Prompts Request and List Prompts Result for discovering available prompts, Read Resource Request and Read Resource Result for accessing server resources, List Tools Request and List Tools Result for discovering available tools, and Initialize Request and Initialize Result for establishing the connection. Each request expects exactly one result. If the server encounters an error, it returns an error result rather than leaving the request unanswered.