MCP Subfinder Server

The MCP Subfinder Server bridges the powerful, community‑maintained subdomain enumeration tool ProjectDiscovery Subfinder with AI assistants through the Model Context Protocol. By exposing Subfinder’s capabilities as a JSON‑RPC service, developers can embed deep reconnaissance into conversational agents without having to manage the complexities of command‑line execution or parsing raw output. This server solves a common pain point in security workflows: the need for a reliable, automated source of subdomain data that can be queried on demand from within an AI‑driven environment.

At its core, the server receives JSON‑RPC requests, translates them into Subfinder commands, and returns structured results. Clients can initialize the connection, list available tools, and invoke subdomain enumeration with optional parameters such as timeouts, recursion depth, or source filters. The server also supports provider configuration, allowing users to inject API keys for premium data sources, thereby expanding the breadth and accuracy of discovered subdomains. Detailed logging is built in, so troubleshooting and audit trails are straightforward—an essential feature for compliance‑heavy security operations.

Key capabilities include:

• Recursive enumeration: Expand beyond first‑level subdomains to uncover deeper infrastructure layers.
• Source filtering: Enable or disable specific passive data sources, giving fine‑grained control over the breadth of results.
• Configurable timeouts and threading: Balance speed against resource usage, tailoring the tool to diverse environments from lightweight CI pipelines to large‑scale threat hunting platforms.
• JSON‑structured output: Results are returned as plain JSON, ready for further processing or direct display in an AI assistant’s interface.

Typical use cases span from automated penetration‑testing workflows—where a chatbot can prompt the server to enumerate subdomains for a target domain—to real‑time threat intelligence dashboards that refresh subdomain lists on demand. Security teams can also integrate the server into continuous integration pipelines, ensuring that every new deployment is immediately scanned for exposed subdomains. Because the MCP interface is language‑agnostic, any AI assistant that understands JSON‑RPC can harness Subfinder’s power without custom adapters.

What sets this MCP server apart is its lightweight wrapper design: it leverages Subfinder’s mature ecosystem while abstracting away the intricacies of configuration, API key management, and result parsing. Developers benefit from a single, stable endpoint that can be called from any programming language or AI platform, enabling seamless integration into broader automated security workflows.