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OpenPhone MCP by usefulapi
io.usefulapi/openphone in the official MCP registry.
Endpoint https://openphone.usefulapi.io/mcp. Source: github.com/m190/usefulapi-mcp.
The registry describes it as: Send and read OpenPhone messages, calls, contacts and phone numbers.
We read its 16 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
openphone_list_phone_numbers openphone_list_users openphone_list_contacts openphone_get_contact openphone_get_contact_custom_fields openphone_list_conversations openphone_list_messages openphone_get_message openphone_send_message openphone_list_calls openphone_get_call openphone_get_call_summary openphone_get_call_transcript openphone_get_call_recordings openphone_list_webhooks openphone_create_contact
Run this server? Show the check in your README
The badge reflects the latest weekly read: 
[](https://lazaretto.dev/mcp-registry/io-usefulapi-openphone)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.