Home / MCP registry index / com.tallyfern/rates
Tallyfern Rates (Canada)
com.tallyfern/rates in the official MCP registry.
Endpoint https://mcp.tallyfern.com/mcp.
The registry describes it as: Read-only Canadian GST/HST rates, small-supplier check and CRA allowance rates, with CRA sources.
We read its 5 tools on 2026-10-26. Nothing in them matched our tool-poisoning rules. It also sets server instructions, text a client puts in front of the model on connect; those were read too.
A clean read means these rules found nothing, not that the server is harmless. A server can change its tools at any time, which is why the index reads it again every week.
Tools it advertises
gst_hst_small_supplier_check gst_hst_rate_by_province cra_automobile_allowance_rate cra_meal_travel_allowance ontario_hst_basics
Run this server? Show the check in your README
The badge reflects the latest weekly read: 
[](https://lazaretto.dev/mcp-registry/com-tallyfern-rates)How this was checked
Lazaretto connects to the endpoint the way any MCP client does, asks the server to introduce itself and list its tools, and reads every name, description, parameter schema and server instruction for tool poisoning: hidden directive blocks, orders to read local secrets, parameters built to carry secrets or the conversation out, orders that redirect another server's tools, and invisible characters. It never calls a tool. What we found across the registry.
To run the same check every time Claude Code adds a server, install the free lazaretto-guard plugin. Browse every server in the index.