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Rex Software MCP by usefulapi

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

The registry describes it as: Read contacts, listings, tenancies and tasks; create a person contact, note or reminder.

We read its 33 tools on 2026-10-31. 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.

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 rex-software https://rex-software.usefulapi.io/mcp

Cursor: ~/.cursor/mcp.json

{
  "mcpServers": {
    "rex-software": {
      "url": "https://rex-software.usefulapi.io/mcp"
    }
  }
}

VS Code

code --add-mcp '{"name":"rex-software","type":"http","url":"https://rex-software.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 jamesdfinance-dev/lazaretto-plugins
claude plugin install lazaretto-guard@lazaretto-plugins

Tools it advertises

rex_get_user_profile rex_list_accessible_accounts rex_describe_search_fields rex_list_value_lists rex_get_value_list rex_autocomplete_contacts rex_autocomplete_listings rex_search_contacts rex_search_listings rex_search_properties rex_search_leads rex_search_appraisals rex_search_tenancies rex_search_reminders rex_search_appointments rex_search_notes rex_search_deals rex_search_activities rex_search_listing_events rex_search_users rex_search_campaigns rex_get_contact rex_get_listing rex_get_property rex_get_lead rex_get_appraisal rex_get_tenancy rex_get_note rex_get_deal rex_get_reminder rex_create_contact rex_create_note rex_create_reminder

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 (2026-10-31): b184c398ae3ff5f6. 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.

Run this server? Show the check in your README

The badge reflects the latest weekly read:

Markdown

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

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.