Subdomain API

app.subdomainPublished by subdomain.appOfficial publisherv1.0.1Updated Oct 24, 2026

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

VerifiedStreamable HTTPWeb executableWeb Search & ScrapingSecurity & Monitoring

Overview

AI-generated overview

Lets an assistant list or count the known subdomains of a root domain from passive, historic observation data.

What you can do
Exposes two tools over a remote endpoint: find_subdomains returns the known hostnames under a root domain, and count_subdomains returns only the total number of distinct subdomains without a list. The data is passive rather than actively scanned, so it reflects historic observations and may include subdomains that no longer resolve or are no longer live. Results are point-in-time snapshots that change as new subdomains are observed.
When to use it
Useful when you want a quick view of a domain's known subdomains or the size of its attack surface without running your own enumeration. The count tool is cheap and low-token when only a number is needed.
Requirements
A remote MCP endpoint at the provider's API host, reached over streamable HTTP. No packages, environment variables, headers or authentication are declared, but network access to the endpoint is required.
Before you install
Results are passive and historic, so they may list subdomains that are no longer live and should not be treated as current. Counts and lists are point-in-time and change over time, so re-query when freshness matters.

Installation

In SourceWeft

  1. Open Subdomain API in the dashboard and add it to a workspace.
  2. Enable the server for the chats that should use its tools.

Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.

Use with an agent

Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.

Read https://sourceweft.com/mcp/app.subdomain%2Fsubdomains/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.

Read the install guide the agent follows

Other MCP clients

Add this to your client's mcpServers config.

{
  "mcpServers": {
    "subdomain-api": {
      "type": "http",
      "url": "https://api.subdomain.app/mcp"
    }
  }
}

Tools

2

find_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`.

Parameterslimitdomainrequired

count_subdomains

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.

Parametersdomainrequired

Version history

1
  1. v1.0.1LatestSep 16, 2026

Score

83% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

  • Reached in the last 30 daysRequired25 pts
  • Auth declaredRequired10 pts
  • Tools listedRequired15 pts
  • DescriptionRequired15 pts
  • Logo10 pts
  • Documentation15 pts

    Declare a GitHub repository with a README, or serve resource_documentation in the OAuth protected-resource metadata.

  • LicenseNot applicable

    A hosted service is used under its provider's terms, so no license is expected here. This check is left out of the percentage.