"Services or tools available for free without requiring an API key" matching MCP servers:

Community MCP server for the Cymulate security validation platform. It exposes the full Cymulate REST API (337 endpoints) as 106 semantic tools for BAS, exposure validation, attack surface management, and platform administration.

Provides a disposable, hardened Kali Linux sandbox with an MCP interface for LLM-driven security analysis of REST APIs, confining blast radius via container isolation.

GDB Enhanced Features MCP server for remote debugging and CTF exploitation with 41 specialized tools including ROP search, format-string detection, and memory patching.

Enables MCP clients to invoke common Kali Linux pentesting tools directly as tool calls, with each binary executed safely without a shell.

Two-way Burp Suite MCP bridge enabling AI agents to capture traffic, analyze endpoints, queue scans, and send findings back to Burp.

Enables AI assistants to perform automated security audits on APIs, detecting BOLA/IDOR vulnerabilities by comparing responses across user tokens.

Scan-as-a-Service for MCP servers. Wraps the compuute-scan static security scanner with HTTP and MCP endpoints to analyze public GitHub repos for MCP-specific vulnerabilities.

Integrates 7 security tools (nmap, nuclei, dirsearch, sqlmap, hydra, Acunetix, Metasploit) via MCP protocol for AI-assisted penetration testing with enterprise-grade safety features.

Enables Claude Code to leverage OpenAI models for expert code review, deep architecture analysis, and security audits, with automatic markdown report generation.

Provides security tools (prompt injection detection, CVE lookup, version impact assessment) for MCP clients like Claude.

An MCP Server that enables users to interact with Google's On-Demand Scanning API (v1beta1) through natural language, likely providing capabilities for vulnerability scanning and security analysis of containers and artifacts.

An MCP server that integrates various penetration testing tools, enabling security professionals to perform reconnaissance, vulnerability scanning, and API testing through natural language commands in compatible LLM clients like Claude Desktop.

An MCP server that integrates multiple security and reconnaissance tools (Nmap, Cariddi, ParamSpider, Metasploit, web scraping) for AI systems, enabling automated network scanning, API discovery, vulnerability testing, and remote access via ngrok.

A production-ready HTTP API server for security testing and reconnaissance, integrating nmap, cariddi, paramspider, metasploit, and web scraping via FastAPI. It supports optional ngrok tunneling and exposes tools through REST endpoints.

Exposes a hardened Docker container with Kali Linux security tools (nmap, sqlmap, dig, whois, etc.) as MCP tools, enabling network reconnaissance, web analysis, and vulnerability scanning through natural language commands.

Offers a control surface for AI agent security with four independent checks: source-code scanning, tenant isolation, LLM content verification, and deploy gating. Currently in pre-release, with no functional scanning engines yet.

Enables ethical security testing and attack surface management through SSL certificate validation, CVE queries, subdomain enumeration, security header analysis, and comprehensive reconnaissance capabilities. Designed for authorized penetration testing workflows with responsible disclosure practices.

Enables agents to inspect web pages for Cloudflare Turnstile challenges without an API key, and clear Turnstile or WAF challenges using a SolveGate API key.

Unified MCP server that gives AI agents security tools to audit MCP configs, redact secrets/PII, vet skills, check dependencies, and scan networks.

Integrates ProjectDiscovery security tools to perform automated reconnaissance, subdomain discovery, and vulnerability scanning. It enables comprehensive bug hunting workflows by chaining tools like subfinder, naabu, and nuclei into a unified pipeline.