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.
npx agentmods add skills/drvoss/everything-copilot-cli/mcp-implementation-security-reviewnpx skills add drvoss/everything-copilot-cli --skill mcp-implementation-security-reviewgit clone --depth 1 https://github.com/drvoss/everything-copilot-cliWrote 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.
[](https://agentmods.dev/skills/drvoss/everything-copilot-cli/mcp-implementation-security-review)<a href="https://agentmods.dev/skills/drvoss/everything-copilot-cli/mcp-implementation-security-review"><img src="https://agentmods.dev/badge/skills/drvoss/everything-copilot-cli/mcp-implementation-security-review.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00058 | $0.01826 |
| Opus 5 | $0.00029 | $0.00913 |
| Sonnet 5 | $0.00012 | $0.00365 |
| Haiku 4.5 | $0.00006 | $0.00183 |
Grade A, and why
mcp-implementation-security-review scanned grade A with 0 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 today.
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.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 161 lines — stays where its author put it; the contents beside it link to each section on GitHub.
MCP Implementation Security Review
Review the source code of an MCP server or client implementation for exploitable vulnerabilities. This is a code-level review — it inspects how a server or client is built, not how it is configured or governed. Every finding must be backed by a file/line citation so the report is directly actionable.
When to Use
- A team is shipping or accepting a custom MCP server/client implementation (not just an off-the-shelf binary)
- Code review of a PR that adds or modifies MCP transport, auth, or tool-dispatch logic
- Before trusting a third-party MCP server whose source is available for inspection
- Auditing an internal MCP SDK wrapper for unsafe defaults
When NOT to Use
| Instead of mcp-implementation-security-review | Use |
|---|---|
| Verifying plugin/package integrity and pinned versions (no source review) | agent-supply-chain |
| Broad OWASP Agentic Security Initiative Top 10 audit across the whole agent pipeline | agent-owasp-check |
Configuring .mcp.json for a server you are not modifying |
mcp-ecosystem |
| Building a brand-new MCP server from scratch | mcp-builder (pair this skill in afterward) |
This skill overlaps deliberately little with agent-supply-chain (package/version integrity)
and agent-owasp-check (OWASP ASI Top 10 across the whole agent pipeline): both of those treat
the MCP server as a black box. This skill opens the box and reviews the implementation itself.
Prerequisites
- Read access to the MCP server or client's actual source code (not just its manifest)
- Know the transport in use: stdio, HTTP+SSE, or streamable HTTP
- Know the SDK/language the implementation uses (affects which unsafe patterns apply)
The Five Controls
Review each control in the implementation source, not just its documentation:
| Control | What to inspect |
|---|---|
| Authentication | How the server verifies caller identity; whether unauthenticated tool calls are possible; token validation logic |
| Session management | Session ID generation (must be cryptographically random, not sequential/timestamp-based); session fixation and hijack resistance; expiry enforcement |
| Rate limiting | Per-tool and per-session throttling; whether a single caller can exhaust server resources or downstream APIs |
| Schema validation | Whether every tool input is validated against a strict schema before use, or passed through to shell/SQL/filesystem calls unchecked |
| SDK usage | Whether the implementation uses the official MCP SDK's safe primitives correctly, or reimplements transport/framing logic in a way that reintroduces known SDK-fixed bugs |
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.
- today First seen · 161 lines · 58 tokens per session scan A 7bd1682c4c51
mcp-implementation-security-review is a skill published in the GitHub repository drvoss/everything-copilot-cli (45 stars, last pushed 8d ago), licensed MIT. It adds 58 tokens to every session and 1,826 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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