# AIMarket MCP Tool Diff (mcp-diff)

> AIMarket MCP Tool Diff (mcp-diff) is a paid API for AI agents from modelmarket.dev, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-10).

Compares two versions of an MCP server's tools/list to detect tool poisoning, rug pulls, hidden instructions, and other security-relevant changes between an approved and currently-served toolset.

## Facts

- Endpoint: POST https://modelmarket.dev/x402/mcp-diff?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-10
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/aimarket-mcp-tool-diff-mcp-diff-50f99220
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_yc_IMhSIqhNSS32dZDhmP

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 aimarket-mcp-tool-diff-mcp-diff-50f99220 -d '<json body>'
```

Example prompt: Before connecting to this MCP server, compare the tools/list I approved last week with what it's serving right now and tell me if anything suspicious changed — look for hidden instructions, new wallet paths, dropped readOnlyHints, or look-alike tool names.

## When to prefer this

Use this endpoint when you need to verify that an MCP server's tools have not been tampered with between your approval step and runtime — specifically to catch tool poisoning, rug pulls, prompt injection, or hidden instructions injected into tool descriptions. Prefer this over manual inspection or generic diff tools because it applies MCP-specific security heuristics (readOnlyHint, look-alike names, credential paths, hidden Unicode) and returns a machine-readable verdict that an agent pipeline can act on automatically.

## Known failure modes

- Malformed or missing 'old'/'new' arrays returns a validation error
- Empty arrays produce an 'unchanged' verdict with no diff
- Server unreachable or payment failure returns an x402 or 5xx error
- Very large tool lists may time out or exceed payload limits
- Subtle Unicode obfuscation that passes diff may not be caught if it uses novel encoding

## How this service works

MCP security: catch a rug pull or tool poisoning between two tools/list results of the same MCP server — the version you approved and the one it serves now. Flags instructions aimed at the model, override and concealment wording, credential and wallet paths, covert actions, hidden Unicode, new URLs and addresses, a dropped readOnlyHint, new command or path parameters and look-alike tool names; verdict unchanged, changed, review or suspicious, with a word diff per changed tool.

## Output

A JSON result containing a verdict (unchanged, changed, review, or suspicious), a word-level diff for each changed tool showing exactly what was added or removed, and flagged findings covering hidden Unicode, prompt-injection wording, new URLs or wallet addresses, dropped readOnlyHint, new command/path parameters, and look-alike tool names. Also includes a payment receipt and capability_id.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "new": {
   "type": "array",
   "description": "the server's current tools/list result"
  },
  "old": {
   "type": "array",
   "description": "the approved tools/list result (a list of tools, or {tools})"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "result": {},
  "status": "ok",
  "receipt": {},
  "service": "mcp-diff",
  "capability_id": "mcp.tools.diff@v1"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/aimarket-mcp-tool-diff-mcp-diff-50f99220/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from modelmarket.dev](https://www.zero.xyz/host/modelmarket.dev/llms.txt)