# PreFlight Checker — MCP Server Safety Audit

> PreFlight Checker — MCP Server Safety Audit is a paid API for AI agents from x402-api-catalog.onrender.com, paid per call via x402, $0.06/call, status unknown (last checked 2026-09-14).

Performs a live MCP handshake plus static analysis of every tool's name, description, and schema to detect tool-poisoning, prompt injection, and dangerous capability combinations, with optional GitHub supply-chain signal.

## Facts

- Endpoint: GET https://x402-api-catalog.onrender.com/api/mcp-audit
- Price: $0.06/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/preflight-checker-mcp-server-safety-audit-0a894951
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ZVUHxij6K1krV37M2cjj0

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability preflight-checker-mcp-server-safety-audit-0a894951
```

Example prompt: Can you run a full safety audit on this MCP server at https://my-mcp-server.example.com — check for prompt injection, tool poisoning, hidden unicode, and dangerous capability combos? Also fold in a supply-chain check for my-org/my-repo while you're at it.

## When to prefer this

Use this endpoint when you need to vet an MCP server before connecting an AI agent to it, especially when the server is third-party, open-source, or untrusted. It is the right choice over generic HTTP health checks because it performs a real MCP protocol handshake and specifically targets AI-agent attack vectors: tool poisoning, hidden unicode, prompt injection in schemas, and dangerous capability bundling. If you also have a GitHub repository for the MCP server, pass it to get a software supply-chain risk signal in the same call.

## Known failure modes

- MCP server URL unreachable or not responding to initialize handshake — audit fails with connection error
- Target server does not speak streamable-HTTP MCP transport — handshake fails
- GitHub repo not found or rate-limited — supply-chain signal omitted from results
- Malformed URL input — returns validation error
- Server times out during tools/list enumeration — partial results or error returned

## How this service works

MCP server safety audit: completes a real initialize+tools/list handshake, then statically scans every tool's name/description/schema for hidden unicode (tool-poisoning), prompt-injection-style phrasing, and tools that quietly combine multiple high-privilege capabilities (network+filesystem+exec+credential access). If a GitHub repo is supplied, folds in a real software-supply-chain signal too.

## Output

Returns a safety score, a verdict (e.g. pass/warn/fail), and detailed findings including any detected hidden unicode characters, prompt-injection-style phrasing in tool names or descriptions, tools that combine multiple high-privilege capabilities (network, filesystem, exec, credential access), and optionally a GitHub supply-chain signal for the linked repository.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "url"
     ],
     "properties": {
      "url": {
       "type": "string",
       "description": "base URL of the MCP server (streamable-HTTP transport)"
      },
      "repo": {
       "type": "string",
       "description": "optional owner/repo to fold in a GitHub supply-chain signal"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "url": {
       "type": "string"
      },
      "score": {
       "type": "number"
      },
      "verdict": {
       "type": "string"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "url": "https://mcp.example.com/mcp",
  "score": 90,
  "verdict": "healthy: no red flags found",
  "findings": [],
  "tools_found": 3
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/preflight-checker-mcp-server-safety-audit-0a894951/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-api-catalog.onrender.com](https://www.zero.xyz/host/x402-api-catalog.onrender.com/llms.txt)