The Model Context Protocol (MCP) gives agents a standard way to call external tools and APIs; MCP security is what governs those calls.
Why MCP is a security surface
A prompt produces text; a tool call acts on the world — it can read a database, send a message, or move money. That makes the tool call one of the most consequential surfaces in an agentic system, for three reasons:
- Real-world impact — the blast radius of a bad tool call is operational, not conversational.
- Toxic combinations — individually safe tools can be chained into something harmful (read a secret with one, send it out with another). No single call looks malicious; the sequence is the exploit.
- Exfiltration paths — a hijacked agent can use a legitimate tool as the channel for data to leave.
Proxying vs. governing MCP
Many tools "support MCP" by proxying — passing tool calls through and logging them. That's not security. Governing MCP means making the decisions a proxy skips:
- Per-tool authorization — explicit rules for which agents may call which tools, and how.
- Egress allowlist — constrain where a tool is allowed to reach; off-list destinations are blocked.
- Inspection of the call itself — scan tool calls for abuse and toxic-combination patterns.
- Full lineage — an audit record of which agent called which tool, with what, and when.
How to secure MCP
Apply least privilege to agents the way you would to service accounts, inspect every tool call as untrusted, allowlist egress, and keep a tamper-evident audit trail. TrustGate does this on the ingress-tool surface, and can also compile any internal REST API into a governed MCP tool from its OpenAPI spec. See Govern MCP, don't just proxy it.
FAQ
What is the Model Context Protocol (MCP)? An open standard that gives AI agents a common interface to call external tools, data sources, and APIs.
Isn't logging MCP traffic enough? No — logging is after-the-fact visibility. Security requires authorizing and inspecting each call before it executes, plus an egress allowlist to contain misuse.