Lesson 3: When an MCP server works against you
19 min read·13 Oct 2026
Module 4 · Lesson 3 · About 50 minutes · Needs: Lesson 2 (an MCP server and a client) and Module 3's tools
The situation
Week 5. BrightCart's tools now run behind its own MCP server. Request R-1005 has no good answer: Tom Becker asks "Where is my TV?", and the agent cannot see the courier's tracking. Priya finds ParcelTrack, a free third-party MCP server for parcel tracking, and asks you to connect it. Sam wants to read its tool definitions first.
ParcelTrack is made up. The attacks are not: each follows a published pattern. You run each one against the returns desk, then the defence that stops it.