MCP Server Governance and AISPM: Securing the Tool Gateway Layer

TL;DR

• MCP standardizes how AI applications connect to external tools and data sources, which makes it a new posture surface.
• Treat MCP servers as privileged gateways: identity, scopes, audit logs, and change control are mandatory.
• Design for prompt injection realities, including the NCSC “confusable deputy” framing.

What MCP is, and why it matters to AI Security Posture Management

The Model Context Protocol (MCP) is an open protocol for integrating LLM applications with external data sources and tools through MCP servers. That turns tools into callable capabilities. It also means:

• MCP servers can become high-trust bridges into sensitive systems
• token scope mistakes become blast radius problems
• logging and auditability become table stakes

The MCP governance model

Inventory and classification

• Inventory every MCP server, its tools, and connected systems.
• Classify MCP servers by risk: read-only vs write-capable vs admin-capable.

Authentication and authorization

• Require auth for every MCP server, no anonymous access.
• Use scoped tokens per tool and per environment.
• Enforce least privilege and short-lived credentials.

Tool catalog and approvals

• Maintain a catalog of tools exposed via MCP, with owners and risk tiers.
• Require approvals for write and admin tools.
• Define “break-glass” policies and incident procedures.

Logging and auditability

• Log tool calls with full context: requester identity, executor identity, tool name, arguments, outcome.
• Store logs with integrity controls and retention aligned to your governance requirements.

Change control

• Treat MCP changes as integration changes:
  • code review
  • configuration review
  • deployment approvals
  • rollback plans

Prompt injection and confusable deputy risk

Prompt injection is not just a classic injection pattern. The UK NCSC highlights that LLMs can behave like “confusable deputies”, where untrusted inputs can coerce privileged actions. Your MCP governance must assume residual prompt injection risk and reduce blast radius through permissions and approvals.