# ToolFit MCP Server Preflight Checker

> ToolFit MCP Server Preflight Checker is a paid API for AI agents from api.youraitools.co, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-25).

Preflights a remote MCP server URL: checks connectivity, protocol version, OAuth metadata, x402 payment terms, latency, tool count, poisoning patterns, and returns a grade with issues — without ever calling the tools.

## Facts

- Endpoint: GET https://api.youraitools.co/toolfit/v1/check?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-25
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/toolfit-mcp-server-preflight-checker-de3b8776
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ScH6oYEiGCgsgWs4UR-i9

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 toolfit-mcp-server-preflight-checker-de3b8776
```

Example prompt: Before I connect to https://api.example.co/mcp, can you run a preflight check on it — I want to know its grade, whether it needs OAuth or payment, how many tools it has, and if there are any poisoning or compatibility issues?

## When to prefer this

Use this endpoint when an agent or developer needs to vet an unfamiliar or third-party remote MCP server before connecting, paying, or deploying tools from it. It is the right choice when you need a security-oriented preflight that checks for poisoning, OAuth requirements, x402 cost, and protocol compatibility in a single call — without actually invoking any of the server's tools. Prefer it over a generic HTTP health check when MCP-specific concerns (tool inventory, prompt injection, payment gating) are the priority.

## Known failure modes

- Unresolvable or blocked URL — no charge, returns error indicating the server could not be reached
- MCP server does not respond to initialize handshake — returns failure verdict with latency data
- Server returns unexpected protocol version — flagged as compatibility issue in the grade
- Network timeout — returns partial latency data with a failure verdict
- Invalid URL format supplied — returns validation error before attempting connection

## How this service works

MCP server checker API. Preflight a public remote MCP server before connecting or paying: does it answer an MCP initialize, which protocol version, sign-in method (OAuth metadata), x402 payment terms, latency, tool count, token cost, provider compatibility, poisoning patterns in tools and instructions, and a grade with issues. Lists tools only, never calls them. Blocked or unresolvable URLs are never charged.

## Output

A JSON object containing: a letter grade (e.g. A–F), a verdict string (e.g. 'ok'), total latency in milliseconds, MCP protocol version, tool count, OAuth/sign-in metadata, x402 payment terms, provider compatibility notes, and a list of detected issues including poisoning patterns. Blocked or unresolvable URLs return an error without incurring a charge.

## 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"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "url"
     ],
     "properties": {
      "url": {
       "type": "string",
       "description": "Public remote MCP server URL (Streamable HTTP, https), e.g. https://api.youraitools.co/mcp/hub. ToolFit only lists its tools."
      }
     },
     "description": "Search intents: mcp server check, test mcp server, mcp preflight, mcp oauth check, remote mcp validator, mcp server health"
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "grade": {
       "type": "string"
      },
      "tools": {
       "type": "number"
      },
      "verdict": {
       "type": "string"
      },
      "latency_ms": {
       "type": "object"
      },
      "protocol_version": {
       "type": "string"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "grade": "B",
  "tools": 31,
  "verdict": "ok",
  "latency_ms": {
   "total": 361
  },
  "protocol_version": "2025-06-18"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/toolfit-mcp-server-preflight-checker-de3b8776/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.youraitools.co](https://www.zero.xyz/host/api.youraitools.co/llms.txt)