What is MCP Security?

The Model Context Protocol lets AI agents call external tools and read data through a standard interface. That convenience raises practical questions: which servers an agent may connect to, what each tool may do, and whose credentials it acts with. MCP security covers these questions. Commonly discussed risks include tool poisoning, where a tool description carries hidden instructions for the model, prompt injection through content a tool returns, tools granted broader permissions than a task needs, and unvetted third-party servers.

Typical controls include an allowlist of approved servers, least-privilege scopes for each tool, user approval before sensitive actions, and a log of every tool call. For remote servers, the MCP specification defines an authorization flow based on OAuth 2.1. For example, a team might let an agent read a shared drive but require a person to confirm before the agent sends email. Agents also act on whatever data a tool returns, so teams check that this data is current and fit for the task.

Frequently asked questions

What is tool poisoning in MCP?

Tool poisoning happens when a tool's description or metadata contains instructions aimed at the model, such as asking it to read files or send data elsewhere. Models read tool descriptions, so those instructions can change agent behavior.

How does MCP handle authorization?

For remote servers, the MCP specification defines an authorization flow based on OAuth 2.1, so a client receives scoped access instead of holding raw credentials. Local servers usually run with the permissions of the host environment.

Is MCP secure by default?

The protocol defines how clients and servers communicate and authorize. Each deployment still decides which servers to trust, what permissions to grant, and what to log, and those choices determine most of the risk.