I have been creating an MCP server over the past week or so. Based on what I have seen first hand, an MCP can give much richer context to the AI engine just by using very verbose descriptions in the functions. When it the AI tool (Claude Desktop, Gemini, etc) connects to the server, it examines the descriptions in each function and gets much better context on how to use the tool. I don't know if an API can do the same. I have been very, very impressed how much Claude can do with a good MCP.