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Zenbooker MCP by usefulapi
io.usefulapi/zenbooker in the official MCP registry.
Endpoint https://zenbooker.usefulapi.io/mcp. Source: github.com/m190/usefulapi-mcp.
The registry describes it as: Read Zenbooker jobs, customers, invoices and timeslots; add customers and job notes.
We read its 21 tools on 2026-10-21. 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
zenbooker_list_jobs zenbooker_get_job zenbooker_add_job_note zenbooker_list_recurring_bookings zenbooker_get_recurring_booking zenbooker_list_customers zenbooker_get_customer zenbooker_create_customer zenbooker_list_invoices zenbooker_get_invoice zenbooker_list_transactions zenbooker_get_transaction zenbooker_list_services zenbooker_get_service zenbooker_list_territories zenbooker_get_territory zenbooker_list_team_members zenbooker_get_team_member zenbooker_list_service_requests zenbooker_check_service_area zenbooker_get_timeslots
Run this server? Show the check in your README
The badge reflects the latest weekly read: 
[](https://lazaretto.dev/mcp-registry/io-usefulapi-zenbooker)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.