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What is the Model Context Protocol (MCP)?

How to answer it in an AI engineer interview: what is being tested, a step-by-step framework, a sample answer and the mistakes to avoid.

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What the interviewer is testing

Whether you can explain what MCP standardizes, how it relates to function calling, and the trust and permission questions it raises.

Answer framework

  1. Define it: an open protocol, introduced in late 2024, for connecting LLM applications to tools and data sources.
  2. Roles: a host application runs MCP clients that connect to MCP servers.
  3. What servers expose: tools (actions), resources (data to read) and prompts (reusable templates).
  4. Benefit: write an integration once and use it from any compatible application, instead of custom glue per app.
  5. Risks: servers are code you trust with data and actions, so review them, scope credentials and watch for prompt injection in returned content.

Sample answer

MCP is an open protocol for connecting LLM applications to external tools and data. Before it, every application wrote its own integration for each service, so connecting several apps to several systems meant a lot of one-off glue code. With MCP, a service exposes an MCP server once and any compatible host, such as a chat app or an IDE assistant, can connect to it through an MCP client.

A server can expose three things: tools the model can call, resources the application can read as context, and prompt templates. The host discovers what is available at runtime and passes tool definitions to the model. Function calling is still how the model asks for an action; MCP standardizes how those tools are described, discovered and invoked across applications.

The main interview point I would add is security. An MCP server can read data and take actions, so I treat installing one like adding a dependency with credentials: use trusted or reviewed servers, give each the narrowest scopes, require confirmation for destructive actions, and treat text returned by tools as untrusted input that could contain injected instructions.

Likely follow-ups

Does MCP replace function calling? No; the model still requests calls in its function-calling format, while MCP standardizes how the host finds and runs the tools.

Common mistakes

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Related questions

Based on question #43 in the full question bank.