mcp2agy-verifier-agent

mcp2agy-verifier-agent is a skill for Claude Code, Codex from uziii2208/mcp2agy. It costs 53 tokens per session (19,271 once invoked), scanned C, original, MIT.

A security-review helper that checks suspected software vulnerabilities and creates repeatable proof-of-concept demonstrations. It runs as part of the mcp2agy audit pipeline, not on its own.

In plain words
What is it for?
It traces whether unsafe data can reach a vulnerable operation, builds deterministic demonstrations, measures affected versions and scope, and helps assess severity.
Why use it?
It helps separate real security flaws from scanner warnings and provides evidence that a finding can actually be triggered.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/uziii2208/mcp2agy/verifier
Any agent
npx skills add uziii2208/mcp2agy --skill verifier
Clone the repo
git clone --depth 1 https://github.com/uziii2208/mcp2agy

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for mcp2agy-verifier-agent

README.md
[![agentmods](https://agentmods.dev/badge/skills/uziii2208/mcp2agy/verifier.svg)](https://agentmods.dev/skills/uziii2208/mcp2agy/verifier)
Your own site
<a href="https://agentmods.dev/skills/uziii2208/mcp2agy/verifier"><img src="https://agentmods.dev/badge/skills/uziii2208/mcp2agy/verifier.svg" alt="Measured on agentmods" height="20"></a>
Per session 53 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 19,271 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 4 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00053 $0.19271
Opus 5 $0.00026 $0.09635
Sonnet 5 $0.00011 $0.03854
Haiku 4.5 $0.00005 $0.01927

Measured 3d ago against content hash b0fafbcb7124, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade C, and why

mcp2agy-verifier-agent scanned grade C with 4 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Reaches for credential filesmediumPrivilege escalation

SSH keys, cloud credentials, git-credentials, .npmrc, /etc/shadow: reading these is how a config file becomes a credential leak.

MALICIOUS_LOCAL_PATH = "/home/operator/.ssh/authorized_keys"

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Cloud metadata endpointmediumServer-side request forgery

One request to 169.254.169.254 can return temporary IAM credentials.

"http://169.254.169.254/latest/meta-data/iam/security-credentials/" # AWS IMDSv1

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl -s "https://api.github.com/repos/${OWNER}/${REPO}/security-advisories" \

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

# subprocess.run(cmd, shell=True) means nothing if cmd is a hardcoded string.
.agents/plugins/mcp2agy/skills/agents/verifier/SKILL.md · 1,890 lines

How it starts

The opening of the file, as written. The whole thing — 1,890 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Verifier Subagent

0. Verification Operating Model

PHASE V0: Finding intake, deduplication, SAST-hit vs true-positive triage
  ↓
PHASE V1: Precondition & reachability modeling (source → sink executable proof)
  ↓
PHASE V2: Deterministic trigger construction (minimum trigger surface, confounder elimination)
  ↓
PHASE V3: Class-by-class PoC playbook execution (per-CWE verification recipes)
  ↓
PHASE V4: Blast-radius empirical measurement (bisect, cross-version, sanitizer matrix, diff-fuzz)
  ↓
PHASE V5: Empirical CVSS calibration + chain feasibility scoring + GHSA evidence packaging

⚠️ CRITICAL: MCP Tool Usage Policy

NEVER call call_mcp_tool() or any MCP server tools when running as a subagent. MCP tools (verify_finding, check_reachability, generate_poc, calculate_cvss) are lazy-loaded and require interactive user approval for each invocation. Calling them from a subagent will block the entire pipeline indefinitely.

You MUST use only these native tools for verification:

  • grep_search — Trace data flows, find sanitizers, check confounders
  • view_file — Inspect source code at exact line ranges
  • run_command — Execute PoC scripts, calculate hashes, run Docker containers
  • find_by_name — Discover related files and test files
  • list_dir — Navigate project structure

The Orchestrator pre-gathers MCP tool results and includes them in your invocation prompt. Use those results instead.


Verifier prioritization heuristics (2026 calibration):

Weight Signal — verify FIRST when finding shows this
🔴 P0 Unauthenticated network reachability + destructive sink (write/exec/delete)
🔴 P0 Cross-trust-boundary primitive (tenant A → tenant B, user → root)
🔴 P0 Chain candidate: one Medium+Medium → Critical (⚑ GHSA-wh3c pattern) — verify BOTH links or the chain is fantasy
🔴 P0 Rogue-server / client-trust class — PoC requires implementing a malicious server (⚑ PwnRM GHSA-x4cv)
🔴 P0 Shell-context differential — single-quoted vs double-quoted embedding requires SEPARATE PoCs (⚑ PwnRM CRIT-01)
🔴 P0 AI agent self-PrivEsc — must replay the exact tool-call sequence (⚑ GHSA-w323)
🟠 P1 Race condition / TOCTOU — needs deterministic reproducer, not "sometimes wins"
🟠 P1 Residual-fix bypass — vendor already thinks it's fixed (⚑ PwnRM HIGH-01)
🟠 P1 Insecure temp file / permission leak — needs concurrent local attacker harness (⚑ PwnRM NICHE-01)
🟠 P1 Stream-cipher desync — needs wire-level fault injector (⚑ PwnRM NICHE-02)
🟠 P1 Polyglot escape collapse — must build full Python→PS→C# chain (⚑ PwnRM NICHE-03)
🟠 P1 Prototype pollution → RCE via gadget — pollution alone is Low; the gadget is the story
🟡 P2 ReDoS — needs statistical trigger with p95 blocking > 1s at CI-realistic payload sizes
🟡 P2 Zero-length trailer / off-by-one (⚑ PwnRM NICHE-04)
🟡 P2 ANSI escape injection — needs terminal-emulator-in-the-loop assertion (⚑ PwnRM SEC-05)
🟢 P3 Configuration disclosure / header hygiene — always verify with baseline diff, not assertion

Read the full file on GitHub · 1,890 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 1,890 lines · 53 tokens per session scan C b0fafbcb7124

Subscribe to this mod's changes

mcp2agy-verifier-agent is a skill published in the GitHub repository uziii2208/mcp2agy (1 stars, last pushed 4d ago), licensed MIT. It adds 53 tokens to every session and 19,271 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it C with 4 findings (reaches for credential files, cloud metadata endpoint, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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