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Acuity Scheduling MCP by usefulapi
io.usefulapi/acuity-scheduling in the official MCP registry.
Endpoint https://acuity-scheduling.usefulapi.io/mcp. Source: github.com/m190/usefulapi-mcp.
The registry describes it as: Read appointments, types, calendars and availability; create, cancel or reschedule bookings.
We read its 18 tools on 2026-10-22. 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
acuity_list_appointments acuity_get_appointment acuity_list_appointment_types acuity_list_calendars acuity_availability_dates acuity_availability_times acuity_availability_classes acuity_list_clients acuity_list_forms acuity_list_products acuity_list_orders acuity_list_blocks acuity_list_labels acuity_get_me acuity_create_appointment acuity_cancel_appointment acuity_reschedule_appointment acuity_create_client
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The badge reflects the latest weekly read: 
[](https://lazaretto.dev/mcp-registry/io-usefulapi-acuity-scheduling)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.