Agent Skill Scanner
agent-skill-scanner MCP Server
Last updated: 2026-03-31
Scan OpenClaw SKILL.md and Model Context Protocol (MCP) tool definition files for security vulnerabilities — directly from Claude Code.
22 detection rules across prompt injection, capability escalation, data exfiltration, encoded payloads, and composition risks. This is the only scanner targeting agent skill file formats specifically. Generic Static Application Security Testing (SAST) tools produce zero detections on these formats.
Install
Requires Python 3.10+ and the scanner engine:
pip install agent-skill-scanner
Configure in Claude Code
Add to your Claude Code MCP settings:
{
"mcpServers": {
"agent-skill-scanner": {
"command": "python3",
"args": ["/path/to/agent-skill-scan-mcp/server.py"]
}
}
}
Replace /path/to/ with the actual path where you cloned this repo.
Tools
scan_skill_file
Scan a single skill file for security vulnerabilities.
scan_skill_file(file_path="/path/to/SKILL.md")
Returns findings with severity, rule ID, description, and evidence.
scan_directory
Recursively find and scan all agent skill files in a directory.
scan_directory(directory_path="/path/to/skills/")
Returns aggregated findings across all discovered skill files.
What it detects
22 rules across 5 categories:
| Category | Examples |
|---|---|
| Prompt injection | System prompt override, role hijacking, instruction injection |
| Capability escalation | Privilege escalation, shell spawning, persistence mechanisms |
| Data exfiltration | Credential access, environment variable reads, outbound transfer |
| Encoded payloads | Base64 commands, hex payloads, obfuscated strings |
| Composition risks | Unrestricted tool chaining, cross-skill data flow, trust violations |
Differentiator
This scanner targets OpenClaw SKILL.md and MCP tool definition formats — markdown-embedded code and YAML skill configurations that generic SAST tools (semgrep, CodeQL) miss entirely. If you're scanning general Python/JavaScript code, use Snyk or semgrep. If you're scanning agent skill files, this is the only tool that covers the format.
Trust & Security
This server runs locally via stdio. No network calls beyond the initial pip install. No data collection. No telemetry.
Source is fully auditable in this repo. The scanner engine source is at github.com/rexcoleman/agent-skill-scanner.
Limitations
- Pattern-based detection only — no semantic analysis
- Designed for OpenClaw SKILL.md and MCP tool definitions
- Rules cover known attack patterns from published research, not zero-days
Links
- Scanner (PyPI): agent-skill-scanner
- GitHub Action: agent-skill-scan-action
- Research: rexcoleman.dev
License
Server Config
{
"mcpServers": {
"agent-skill-scanner": {
"command": "python3",
"args": [
"/path/to/agent-skill-scan-mcp/server.py"
],
"env": {}
}
}
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