nexus-mcp — jpi-guard & PII Guard MCP Server

LLM security APIs for Japanese applications, available as an MCP server.

MCP endpoint: https://mcp.nexus-api-lab.com/
Transport: HTTP (Streamable HTTP / JSON-RPC 2.0)
Homepage: https://www.nexus-api-lab.com
Discovery: https://mcp.nexus-api-lab.com/.well-known/mcp.json

Quick connect

Claude Code / Claude Desktop

claude mcp add --transport http nexus-mcp https://mcp.nexus-api-lab.com/

Or add to your .mcp.json:

{
  "mcpServers": {
    "nexus-mcp": {
      "type": "http",
      "url": "https://mcp.nexus-api-lab.com/"
    }
  }
}

Cursor / Windsurf / other MCP clients

Add to your MCP config:

{
  "nexus-mcp": {
    "transport": "http",
    "url": "https://mcp.nexus-api-lab.com/"
  }
}

Tools

jpi-guard — Prompt Injection Detection

Tool	Description
`check_injection`	Detect prompt injection in user input. Specialized for Japanese (全角バイパス, 丁寧語擬装, indirect injection).
`validate_rag_input`	Gate check before passing input to RAG/LLM pipeline. Returns `safe: true/false`.
`sanitize_content`	Sanitize external content fetched from the web before passing to LLM.
`get_trial_key`	Get a free jpi-guard API key (2,000 req / 30 days, no signup).

Free trial: https://www.nexus-api-lab.com/jpi-guard.html

PII Guard — Japanese PII Detection & Masking

Tool	Description
`pii_scan`	Scan Japanese text for 10 PII categories. Returns `findings[]` + `masked_text` with `[TYPE]` placeholders. No LLM — pure regex + checksum.
`get_pii_guard_key`	Register email and get a free PII Guard key (10,000 req/month, permanent free tier).

PII categories: My Number (mod-11), credit card (Luhn), bank account, passport, phone, email, postal address, date of birth, driver's license, person name.

Free tier: https://www.nexus-api-lab.com/pii-guard.html

Why use this instead of writing your own?

Japanese-specialized — full-width character normalization, polite-language disguise detection, My Number checksum validation
Deterministic — no LLM calls inside the API. Fast, auditable, consistent results
Free to start — no credit card, no signup for trial keys
Edge-deployed — Cloudflare Workers global network, sub-50ms p99

License

MIT — see LICENSE

nexus-mcp