MCP vs everything

MCP gets compared to five things it mostly isn't competing with. Each page below gives the direct answer in the first paragraph, then the table, then when to actually use which.

MCP vs API

A layer on top, not a replacement

APIs expose a product to developers; MCP re-exposes it to AI models. Nearly every MCP server wraps an API.

MCP vs RAG

A protocol vs a technique — complementary

RAG grounds a model in your documents; MCP wires it to live systems. You can run RAG through MCP.

MCP vs A2A

Tools vs teammates — different layers

MCP connects one agent to its tools; A2A connects agents to each other. Serious agent stacks use both.

MCP vs Claude Skills

Know-how vs connections

A Skill teaches the model a procedure from files; an MCP server gives it live access to external systems.

MCP vs function calling

MCP standardizes what function calling started

Function calling is the model-native mechanism; MCP makes the tools discoverable, portable and shareable.

The short version

The Model Context Protocol is plumbing: a standard way for AI assistants to discover and call external capabilities. APIs are what it plumbs into. RAG is a retrieval technique it can carry. A2A operates one layer up, between whole agents. Skills package instructions rather than connections. And function calling is the model-side mechanism MCP builds on. If a comparison page tells you one of these "kills" another, it's selling something.