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fourzerotwo

by fourzerotwo.si · remote · no sign-in to list tools · v1.2.1 · published by si.fourzerotwo

400+ data APIs for agents: UK companies, property, trade, tenders, recalls, sanctions. Free tier

Changes · 1
CompareRegistry entry

3 tools: 1 change things and 2 only read.

Scanned Oct 21, 2026

1 check matched something in the tool definitions. No finding is not a safety guarantee. How the checks work.

claude mcp add --transport http data https://fourzerotwo.si/mcp

Findings

Matches of fixed checks, with the text they matched.

1 warn
  • Warncall_api

    The server marks "call_api" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

    Matched text

    annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":true}; The name "call_api" says "call": a word for a change.

    What this check looks for

Tools

Open a tool for its reasons and full description. Descriptions are the publisher's own words, shown as they are.

3 tools

Changes things 1Claude Code: ask
  • call_apiRun one endpoint by the tool name that search_apis returned, with that endpoint's parameters, and get its data back as JSON (with source and licence attribution).1 finding

    Why it is in this group

    • The name "call_api" says "call": a word for a change.
    • The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.

    Findings

    • Warn

      The server marks "call_api" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

      Matched text

      annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":true}; The name "call_api" says "call": a word for a change.

      What this check looks for
    Description, as the server wrote it
    Run one endpoint by the tool name that search_apis returned, with that endpoint's parameters, and get its data back as JSON (with source and licence attribution). Endpoints with free_tier "free" or "sample" cost nothing within the daily allowance (100 calls/day anonymously, 500 with a free key). Otherwise the result is a payment request: pay in USDC via x402 and retry with _meta["x402/payment"]. Invalid arguments are rejected before any charge, and failed upstream calls are never charged.

    Annotations the server declares

    • title: Call a data API
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: true
Only reads 2Claude Code: allow
  • list_apisOverview of every API group in the catalog: name, category, summary, number of endpoints and whether it has a free tier.No findings

    Why it is in this group

    • The name "list_apis" says "list": a word for reading.
    Description, as the server wrote it
    Overview of every API group in the catalog: name, category, summary, number of endpoints and whether it has a free tier. Always free to call. Use it to browse; use search_apis to find a specific endpoint.

    Annotations the server declares

    • title: List API groups
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: true
  • search_apisFind the right data endpoint for a task.No findings

    Why it is in this group

    • The name "search_apis" says "search": a word for reading.
    Description, as the server wrote it
    Find the right data endpoint for a task. Searches 500+ endpoints (UK legislation, Companies House, property prices, sanctions lists, vehicle tax, weather, earthquakes, arXiv/PubMed/Crossref papers, IP geolocation, GB electricity, ONS/World Bank/ECB economics, and more) by keyword and returns each match's tool name, parameters, price and free_tier. Always free to call. Next step: pass a returned tool name to call_api.

    Annotations the server declares

    • title: Search data APIs
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: true

This is not a safety rating, and no finding is not a safety guarantee. The groups and findings come from fixed checks of the tool definitions the server returned on the date shown, not from its code or what it does when called. How the checks work.

Install

Pinned to version 1.2.1. Values in angle brackets are yours to fill in.

claude mcp add --transport http data https://fourzerotwo.si/mcp

Run in a terminal.

Claude Code permissions

Allow the reads, ask before a change, deny the deletes. Paste into .claude/settings.json.

.claude/settings.json
{
  "permissions": {
    "allow": [
      "mcp__data__search_apis",
      "mcp__data__list_apis"
    ],
    "ask": [
      "mcp__data__call_api"
    ],
    "deny": []
  }
}

Tools that only read are allowed, tools that change things ask first, tools that delete or cancel are denied. It assumes the server is installed as data. Review it before you use it.