# What is MCP, the Model Context Protocol?

An open standard for connecting AI applications to tools and data. A system offered once as an MCP server works in any application that speaks MCP.

- Page: https://tecyfy.com/concepts/model-context-protocol
- Subject: AI agents (https://tecyfy.com/concepts)
- Level: beginner
- Also called: MCP

Without a shared standard, every AI application needs its own connector for every system it talks to. Link 5 assistants to 5 systems and someone builds 25 connectors. The Model Context Protocol, MCP for short, is an open-source standard that replaces them with one shape: a system offers its tools once, as an MCP server, and any application that speaks MCP can use them. Its own documentation compares it to a USB-C port for AI applications.

## The 3 parts

- **Host.** The AI application, such as Claude Code, Claude Desktop or Visual Studio Code.
- **Client.** A connection the host opens for each server it talks to.
- **Server.** A program that offers data and actions. It can run on your own machine, talking through standard input and output, or remotely, over Streamable HTTP.

The messages between them use JSON-RPC 2.0, a plain format for requests and replies.

## What a server offers

- **Tools:** actions the model can ask for, such as searching an issue tracker or creating a calendar event. To the model they are [tools](https://tecyfy.com/concepts/tool-use) like any other, each a name, a description and the inputs it takes.
- **Resources:** data the application can read, such as files or database records.
- **Prompts:** ready-made templates for common jobs.

Claude, ChatGPT, Visual Studio Code and Cursor are among the many applications that can connect to MCP servers.

## Where it fits in an agent

An MCP server does not make a model smarter. It gives the [agent](https://tecyfy.com/concepts/agent) more tool cards. The model still writes a request for a tool, and the host passes it to the server and brings the result back. On the Claude API, the MCP connector lets a request name remote MCP servers directly, with no client code of your own. It handles tool calls only and is in beta.

## What to watch

Every tool a server offers is a card that can be sent with every request. Connect a few servers with many tools each and their cards can fill much of the context before the agent does any work. Tool search, which loads a tool's card only when it is needed, is one answer.

A server is also code that acts with your access. Connect only servers you trust, give each the narrowest access it needs, and ask a person before tools that send, pay or delete. What a server returns is outside content, and it can carry a [prompt injection](https://tecyfy.com/concepts/prompt-injection) like any web page.

## Related

- [Tool Use](https://tecyfy.com/concepts/tool-use): Giving a model a list of things it can ask to have done, such as search the web or read a file. The model asks; the program around it does the work and hands back the result.
- [Agent](https://tecyfy.com/concepts/agent): A model that uses tools in a loop, deciding each next step from what the last one returned, until the task is done.
- [Function Calling](https://tecyfy.com/concepts/function-calling): The developer's name for tool use. The model replies with the name of a function and its arguments in a fixed format, and your code runs it.
- [Prompt Injection](https://tecyfy.com/concepts/prompt-injection): An attack that hides instructions in text a model reads, such as a web page, an email or a file, so the model follows the attacker instead of you.
- [Context Engineering](https://tecyfy.com/concepts/context-engineering): Choosing what goes into a model's context at each step of a task, what to fetch only when needed, and what to clear, note down or summarise as the context grows.

## Sources

- [What is the Model Context Protocol (MCP)?](https://modelcontextprotocol.io/docs/getting-started/intro)
- [Architecture overview](https://modelcontextprotocol.io/docs/learn/architecture)
- [MCP connector](https://platform.claude.com/docs/en/agents-and-tools/mcp-connector)
- [How the agent loop works](https://code.claude.com/docs/en/agent-sdk/agent-loop)
- [Mitigate jailbreaks and prompt injections](https://platform.claude.com/docs/en/test-and-evaluate/strengthen-guardrails/mitigate-jailbreaks)