Field Guide 26: a security review template for MCP permissions, 27 items that walk STRIDE through the threats the MCP specification and published research describe, from lookalike packages and tool poisoning to token passthrough and authorization URL injection. The kit has the review template, a permissions inventory format with a JSON Schema, a checker that flags understated risk, overdue reviews and trifectas across a client's servers, and a tool-list diff with a lockfile that caught 4 errors in a doctored patch release.
When a server is approved for real work, when an upgrade arrives, when you add a server to a client that already has others, and once a quarter for the whole inventory.