MCP Inspector alternative
An MCP Inspector alternative for security review
MCP Inspector is Anthropic's interactive debug UI for testing MCP servers as you build them — point it at a server, see the tools it exposes, click through prompts and resources, watch the JSON-RPC. SkillAudit is a non-interactive security audit that grades the server's source code before you install it. Different stages of the workflow, different questions, both worth running.
TL;DR
MCP Inspector is the right tool for "what does this server expose, and does each tool actually work the way the README claims" — you launch it, it speaks the protocol, you click. It is not a security scanner: there is no SSRF check, no prompt-injection probe, no credential-echo detection, no per-repo grade. SkillAudit answers the security question — "is this server safe to install" — by reading the source code of the tool handlers and grading them across six axes. We scanned 101 of the most-installed MCP servers: 50% had SSRF, 38% had credential-handling findings, 19% earned an A. That signal is invisible to MCP Inspector by design — it's not what Inspector is for.
Note: we audited Anthropic's own modelcontextprotocol/inspector repository and gave it an F because its own server-side code has 10 fetch(url) call sites — see the live report. Honest grading on a tool we use and recommend.
Why teams look for an MCP Inspector alternative for security review
MCP Inspector is excellent at what it's built for: a developer fires it up against a server during build or pre-install evaluation and walks the surface. Tools list, prompt list, resource list, sample arguments, watch the responses, confirm everything claimed in the README is actually wired. As a build-loop tool and a "what does this server even do" reconnaissance step, it's the right product.
But the "do I let an agent install this MCP server in CI" decision is a different question. The reviewer needs to know:
- Does the
fetch_urltool validate the URL host, or does it callfetch(req.url)straight through into our internal network? - Does any handler return
process.envvalues back to the LLM in a debug field? - If the LLM passes a prompt-injection payload as a tool argument, does the handler treat it as data or smuggle it back into the conversation as instructions?
- Has the repo been touched in the last 90 days? Are there 200 unanswered issues?
- Does it actually work on the clients my team uses — Claude Code, Cursor, Windsurf, Codex?
None of those is answerable by clicking through Inspector's UI. The first three need source-code review (or a static + LLM scanner that does it for you). The last two need repo metadata and a manifest review. That's the gap SkillAudit fills.
Three reasons buyers and authors look for an MCP Inspector alternative when the question is security:
- Inspector is a runtime tool, the security question is a code question. Watching a tool's response in Inspector tells you what it returns when you call it nicely. It does not tell you what happens when an LLM passes a prompt-injection payload, or when an attacker passes
http://169.254.169.254/latest/meta-data/as the URL argument. Static analysis of the handler source is what answers those. - Inspector doesn't grade. SkillAudit does. Buyers want one A–F with a paragraph of reasoning. Inspector is structured for exploration, not for ship/no-ship.
- Inspector is interactive; install decisions need to scale. If your team adopts MCP servers, you can't manually walk every server in Inspector before greenlighting it. SkillAudit's report cards are written so the reviewer can read one paragraph and decide.
How SkillAudit is different
SkillAudit is a six-axis static + LLM-assisted scanner built specifically for Claude skills and MCP servers. The six axes — security, permissions hygiene, credential exposure, maintenance, client compatibility, documentation — were chosen by reading the actual source of vendor-official MCP releases that shipped vulnerabilities. The output is a single A–F grade plus a public report card at a stable URL the author can embed as a badge on their README.
Where MCP Inspector is an interactive build-time UI, SkillAudit is a non-interactive, source-reading scanner that runs in seconds against any public GitHub repo, npm package, or uploaded ZIP — and produces a buyer-readable grade. They sit at different points in the install decision workflow.
Side by side
| MCP Inspector | SkillAudit | |
|---|---|---|
| Primary purpose | Interactive debug UI for MCP servers | Non-interactive security + quality audit grading tool-handler code |
| What it reads | Live JSON-RPC traffic against a running server | Source code, env-var usage, README, manifest, repo metadata |
| Static SSRF check on tool handlers | No | Yes — pattern-based check tuned to MCP idioms |
Static command-exec check (shell=True, execSync) | No | Yes — first-class axis |
| LLM-assisted prompt-injection probe | No | Yes — extracts handlers, red-teams them via Claude Haiku 4.5 |
| Credential-echo detection (env var → tool response) | No (you'd see it in the response stream if you tested for it manually) | First-class axis; flags process.env.X in handler return paths |
| Permission-scope review | No | Yes — flags overscoped manifests and undeclared capabilities |
| Maintenance signal (last commit, open issues, advisories) | No | Yes — first-class axis |
| Client compatibility check | Inspector itself is one client; doesn't grade compatibility | Yes — flags non-standard transports + protocol-version mismatches |
| Single A–F buyer grade | No | One letter grade + per-axis pass/warn/fail |
| Public per-repo report card URL | No (Inspector runs locally) | Yes (e.g. /audits/owner-repo/) |
| Public embed badge for authors | No | Yes — skill-grade badge written for marketplace listings |
| Workflow stage | Build / explore / pre-install reconnaissance | Pre-install gate / continuous adoption review |
| Cost | Free, open source (MIT) | Free for 3 audits/month on public repos; $19/mo Pro; $99/mo Team |
What the data says
We ran SkillAudit against 101 of the most-installed Claude skills and MCP servers — the full live board is public and growing. The corpus includes vendor-official releases (Stripe, PayPal, MongoDB, Redis, Cloudflare, AWS, Azure, GCP, Heroku, Notion, Snowflake, Pinecone, Couchbase, Auth0, Resend, Brave, Vectara, Meilisearch, plus the nine official Anthropic MCP language SDKs), popular indie frameworks (FastMCP, mcp-use, mcp-agent), and community releases.
Results: 50% (50/101) shipped SSRF findings, 38% (38/101) had credential-handling findings, 10% (10/101) had command-exec findings, and only 19% (19/101) earned an A grade. Full grade distribution: 19 A · 30 C · 10 D · 42 F. Methodology and per-repo grades are in our research post: The state of MCP server security, 2026.
The relevant point for the Inspector comparison: an MCP server can pass an Inspector walk-through cleanly — every tool returns the documented response, every prompt and resource lists correctly — and still ship 10 fetch(url) SSRF call sites in the handler bodies. Inspector tells you the protocol surface looks healthy; SkillAudit tells you whether the code behind that surface is safe.
When MCP Inspector is still the right choice
Inspector is the right tool for a lot of the MCP install workflow. Specifically:
- You're building an MCP server and need a fast feedback loop. Type-checking and unit tests catch some classes of bug; clicking through Inspector while the server is running catches the others. SkillAudit doesn't replace the build loop.
- You want to see what a third-party server actually exposes. The README claims six tools — Inspector confirms what's actually wired and what each one returns. That's a legitimate pre-install reconnaissance step.
- You're debugging a protocol issue. Inspector shows the JSON-RPC frames in detail. If a client isn't handling a server's response, this is where you reproduce it.
- You're verifying a SkillAudit finding manually. SkillAudit flags an SSRF in a
fetch(url)tool? Open Inspector, passhttp://169.254.169.254/latest/meta-data/as the URL argument, watch what comes back. The two tools compose well.
The most useful framing: MCP Inspector answers "what does this server do and does it work"; SkillAudit answers "is the source code behind it safe to install." Both questions matter; the answers are independent. Inspector is interactive and runtime-driven; SkillAudit is non-interactive and source-driven. They sit on different sides of the install gate.
Workflow
SkillAudit isn't a replacement for MCP Inspector — it's the security gate that runs alongside it. A typical adoption path for someone evaluating a new MCP server:
- Paste the GitHub URL into SkillAudit, get the A–F grade. If it's a hard fail (F on security or credentials), stop here — you don't need Inspector to confirm an SSRF.
- If the grade is acceptable, open Inspector against the running server to walk the actual tool surface. Confirm tool list matches the manifest, sample-call each one, watch responses.
- Drop the SkillAudit badge into your team's MCP allow-list documentation so the next reviewer can see why this server was greenlit.
Indie developers shipping MCP servers can use both at zero cost: Inspector is free indefinitely; SkillAudit's free tier covers your skill grade up to three audits a month, and the public report card you'll get is shareable on your README.
Try SkillAudit on your repo — free
Paste any GitHub URL on the home page, get a graded report card in 60 seconds. Your repo joins the public board only if you opt in; private repos audit through a single-repo OAuth scope, never org-wide.