cypherctrl

Project · Active · started

Securing Agent Tool Use: An MCP Control Catalogue

A vendor-neutral catalogue of controls for agents that call tools through the Model Context Protocol. It covers tool poisoning, confused-deputy access, weak server authentication and over-privileged credentials, organised by where each control sits in the life of a tool call.

The kitsune on its cipher disk, reading CYPHER and CTRL The kitsune on its cipher disk, reading CYPHER and CTRL

Scope

The moment an agent can call tools, a prompt injection stops being a bad answer and becomes an action taken with someone’s credentials. MCP made connecting tools easy; it did not make it safe by default. This project collects the controls that matter and places each one at the point in a tool call where it actually works:

  1. Discovery: which servers and tools an agent is allowed to see, and how tool descriptions are reviewed and pinned.
  2. Authentication and authorisation: whose authority the tool acts with, and how to avoid the confused deputy.
  3. Execution: sandboxing, egress limits, approval for high-impact actions.
  4. Audit: the evidence you need to reconstruct what an agent did and why.

Status

Scoping. Collecting real-world MCP failure modes and mapping them to controls.

Planned artifacts

  • Control checklist across the tool-call lifecycle
  • Approval-policy template for high-impact tool actions
  • Review questions for adopting a third-party MCP server

References