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UnderChat MCP by usefulapi

io.usefulapi/underchat in the official MCP registry. Endpoint https://underchat.usefulapi.io/mcp. Source: github.com/m190/usefulapi-mcp.

The registry describes it as: List WhatsApp chats, contacts and sectors; send, transfer and label chats in UnderChat.

We read its 21 tools on 2026-11-11. 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 about every two weeks.

Connect it

The endpoint answers MCP over HTTP; that is how we read it. Add it to your client:

Claude Code

claude mcp add --transport http underchat https://underchat.usefulapi.io/mcp

Cursor: ~/.cursor/mcp.json

{
  "mcpServers": {
    "underchat": {
      "url": "https://underchat.usefulapi.io/mcp"
    }
  }
}

VS Code

code --add-mcp '{"name":"underchat","type":"http","url":"https://underchat.usefulapi.io/mcp"}'

Some servers ask you to sign in the first time a client connects, or want a key from the people who run them; the server's own docs say which.

Let Claude Code check servers as it adds them

With the free lazaretto-guard plugin installed, when Claude Code adds a server for you or writes one into an MCP config, the plugin reads the server's tools first and asks you if one of our rules matches. Install it, restart Claude Code, then ask it to run the command above.

Install lazaretto-guard

claude plugin marketplace add lazaretto-ai/lazaretto-plugins
claude plugin install lazaretto-guard@lazaretto-plugins

Tools it advertises

underchat_list_chats underchat_search_chats underchat_get_chat_messages underchat_search_chat_messages underchat_get_chat_details underchat_get_unread_summary underchat_list_channels underchat_list_workers underchat_list_contacts underchat_get_contact underchat_find_contact_by_phone underchat_list_label_templates underchat_list_sectors underchat_list_users underchat_get_user underchat_send_text_message underchat_update_chat_status underchat_transfer_chat underchat_set_chat_labels underchat_create_contact underchat_update_contact

Tool changes

We compare every full read of this server with the one before. No change in what its tools say has been seen since we started keeping this record on 2026-10-30.

Fingerprint of its tools at our last full read (2026-11-11): 7cb21309381e53c2. A client can hash the tools it is served the same way and compare; the full value and a hash per tool are in this page as JSON.

Rather than checking back: subscribe to this server's tool changes (a feed, no account and no address needed). Tool names and dates only, never what a tool says.

Run this server? Show the check in your README

The badge reflects the latest read:

Markdown

[![MCP tool check](https://lazaretto.dev/mcp-registry/io-usefulapi-underchat/badge.svg)](https://lazaretto.dev/mcp-registry/io-usefulapi-underchat)

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. How tool poisoning works. What we found across the registry. Check another server.

To run the same check every time Claude Code adds a server, install the free lazaretto-guard plugin. Browse every server in the index.