MCP is a new protocol from anthropic to standardize sharing tools and context with LLMs. Before, the tool calling api from openai was standard but tool makers all built their own mechanisms for defining and sharing tools.

It's a bit of a stretch but MCP is to LLM enabled applications what REST is to web applications.

What was happening before was if you built tools using langchain, you'd have to rewrite them for crewai, cursor, etc. Now, we have a way to share tools, resources, and prompts with applications built using different frameworks.