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FactLot

io.github.9mp96ygnbk-alt/factlot in the official MCP registry. Endpoint https://api.factlot.com/mcp. Source: github.com/9mp96ygnbk-alt/factlot.

The registry describes it as: Cited CRE facts and deterministic calculators for agents: rent, CAM, debt sizing, IRR, parcel IDs.

We read its 42 tools on 2026-11-04. 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 factlot https://api.factlot.com/mcp

Cursor: ~/.cursor/mcp.json

{
  "mcpServers": {
    "factlot": {
      "url": "https://api.factlot.com/mcp"
    }
  }
}

VS Code

code --add-mcp '{"name":"factlot","type":"http","url":"https://api.factlot.com/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

calc_rent_schedule calc_net_effective_rent calc_compare_proposals calc_multifamily_rent_roll calc_percentage_rent calc_cam_reconciliation calc_cam_reconciliation_batch calc_capex_recovery calc_debt_sizing calc_lease_remeasurement_asc842 calc_prepayment_and_defeasance calc_walt calc_npv calc_irr calc_lease_vs_own calc_renew_vs_relocate calc_hotel_metrics calc_dcf_pro_forma calc_direct_cap calc_amortization_schedule calc_equity_waterfall calc_exchange_1031 rules_tx_property_tax_protest_deadline id_parcel id_entity id_space id_building id_document id_parse fact_validate doc_verify_facts doc_abstract_lease doc_compare doc_verify_claim doc_spread_statement doc_check_use_conflict fact_package_create fact_package_verify lease_comp_validate search fetch schema_get

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 (2026-11-04): bd1153505c572516. 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-github-9mp96ygnbk-alt-factlot/badge.svg)](https://lazaretto.dev/mcp-registry/io-github-9mp96ygnbk-alt-factlot)

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.