Subdomain API MCP Server

by subdomain Your server? Claim it

answering

Subdomain API is answering right now. Last checked 3 min ago. It exposes 2 tools.

Find known subdomains of a domain. Passive data; may include historic entries. List or count.

Uptime history 48 days of history

48 days agonow

100.0%

Uptime 24h

92 of 92 checks

Tools

read from the server

366 ms

Response time

average over 24h

open, no key

Access

streamable-http

Nothing serious here today

Today is the operative word: we check Subdomain API every 15 minutes and re-read its code on every release. Watch it and you find out the day that stops being true.

Connect this server

Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 3 min ago.

Claude Code Claude Desktop Codex Cursor VS Code

run in your terminal

claude mcp add subdomains --transport http https://api.subdomain.app/mcp

~/Library/Application Support/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "subdomains": {
      "url": "https://api.subdomain.app/mcp"
    }
  }
}

~/.codex/config.toml

[mcp_servers.subdomains]
url = "https://api.subdomain.app/mcp"

.cursor/mcp.json

{
  "mcpServers": {
    "subdomains": {
      "url": "https://api.subdomain.app/mcp"
    }
  }
}

.vscode/mcp.json

{
  "mcpServers": {
    "subdomains": {
      "url": "https://api.subdomain.app/mcp"
    }
  }
}

Available tools 2

Read directly from the server with tools/list, grouped by what they act on. If a tool disappears, we record the date.

count

count_subdomains

Return only the total number of distinct subdomains known for a domain — no list. Cheap and low-token. Use when the user asks "how many subdomains" or you only need the size of the attack surface. Count includes historic subdomains that may no longer be live. It is a point-in-time figure that changes over time, so treat it as current-as-of-query, not a fixed value.

subdomains

find_subdomains

List known subdomains (hostnames) of a root domain. Data is passive (not active scanning): results are historic observations and may include subdomains that no longer resolve or are no longer live. Results are a point-in-time snapshot that changes over time as new subdomains are observed — re-query rather than caching the result. Use for attack-surface mapping, security recon, asset inventory, or SEO host discovery. Hostnames are returned most-recently-seen first. The response always reports `total` (full distinct count known) and a `truncated` flag, so you can tell when more exist beyond `limit`.

Endpoints

URL	Transport	State	Latency	Checked
https://api.subdomain.app/mcp	streamable-http	answering	231 ms	3 min ago

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Subdomain API — questions

Answers built from our own checks of this server.

What can Subdomain API do?

It exposes 2 tools, read directly from the server on our last check. Among them: count_subdomains, find_subdomains. The full list with descriptions is on this page — we take it from the server itself via tools/list, not from a README. How MCP servers expose tools in the first place →

Is Subdomain API working right now?

We send a real MCP handshake every 15 minutes. Over the last 24 hours 92 of 92 checks got a reply (100.0%), average response time 366 ms. The bar chart above shows every period we have measured.

How do I connect Subdomain API?

Copy the ready config from this page — we generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each with the file path that client actually reads. It is a remote server, so there is nothing to install — the client connects to the address.

Does Subdomain API need an API key?

No. Subdomain API completed a full MCP handshake with us as an anonymous client and listed its tools without asking for anything. All 2 of them are readable on this page. This is what we observed, not what the docs claim.

How fast is Subdomain API?

It answers our handshake in 366 ms on average, which is faster than 42% of all working MCP servers we measure. The comparison comes from our own checks across the whole registry, every 15 minutes.