mcp_subfinder_server
Provides a Model Context Protocol (MCP) server that wraps ProjectDiscovery's subfinder to enumerate subdomains for a given domain via a JSON-RPC interface, including options for recursion, depth, timeouts, and source filtering/exclusion. Includes a /health endpoint for liveness.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
No authentication/authorization is documented for the MCP JSON-RPC endpoint; /health is unauthenticated per examples. Docs mention adding API keys to provider-config.yaml for premium sources, but do not describe secret handling practices (e.g., redaction/logging behavior). TLS is not mentioned; examples use http://localhost.
⚡ Reliability
Best When
You need an on-prem or self-hosted MCP server that can be called by an agent to run subfinder with configurable parameters.
Avoid When
You cannot control network exposure or request sizes, or you require documented idempotency/retry semantics and strict operational guarantees.
Use Cases
- • Automating passive subdomain enumeration workflows via an MCP-compatible client/agent
- • Recursive subdomain discovery with depth and timeout controls
- • Selective enable/disable of subfinder sources for targeted recon
- • Integrating subdomain enumeration into internal tooling using JSON-RPC calls
Not For
- • Production-grade authenticated APIs without additional deployment security
- • Environments requiring strict legal/compliance controls over OSINT source usage (not addressed in the docs)
- • Use cases needing a stable, externally hosted SaaS API with published SLAs
Interface
Authentication
No authentication is described for the JSON-RPC endpoint or /health. The docs indicate local usage (localhost) by curl.
Pricing
Self-hosted open-source project (MIT). Cost is deployment/compute and any costs from configured subfinder sources/providers.
Agent Metadata
Known Gotchas
- ⚠ Subdomain enumeration can be resource-intensive and may take longer than typical agent timeouts; ensure agent-side timeouts align with the server/tool timeout parameters.
- ⚠ No auth is documented; agents should not expose the server publicly without adding network/auth controls.
- ⚠ Recursive enumeration and high timeouts/depth can amplify work and result size; constrain parameters for safer agent runs.
Alternatives
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Scores are editorial opinions as of 2026-04-04.