GrindFree Agent Security

GrindFree Agent Security

MCP server + client snippets for GrindFree’s pay-per-call agent security APIs on Base:

Service	Endpoint	Price	What it does
PromptShield	POST https://promptshield.grindfree.net/v1/screen · /v1/clean	$0.002	Prompt-injection screen + HTML→LLM clean text
CrawlSafe	POST https://crawlsafe.grindfree.net/v1/check	$0.002	robots.txt / X-Robots-Tag crawl gate (SSRF-guarded; not malware scanning)
ToolGuard	POST https://toolguard.grindfree.net/v1/evaluate	$0.002	Pre-tool-call allow | review | deny policy gate
CommandGuard	POST https://commandguard.grindfree.net/v1/command · /v1/sql	$0.001	Shell command + SQL check before execution: allow | warn | block
MemoryGuard	POST https://memoryguard.grindfree.net/v1/screen	$0.002	Screen content before it is written to agent memory (planted instructions, persistence, secrets/PII)
WireShield	POST https://wireshield.grindfree.net/v1/scan	$0.002	Outbound leak check on agent output (zero-click image exfil, URL smuggling, canaries, prompt leakage)
DocShield	POST https://docshield.grindfree.net/v1/scan	$0.004	Hidden instructions in PDF / DOCX / XLSX / PPTX / HTML / Markdown before the agent reads them

Price: per call in USDC (table above) on Base (eip155:8453) via x402 v2.
Wallet: the caller’s Base USDC wallet pays. This repo never ships GrindFree keys.

Contact: [email protected] · @grindfreelabs

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Install / run the MCP server (stdio)

git clone https://github.com/ronin93/grindfree-agent-security.git
cd grindfree-agent-security/mcp-server
npm install

Set the caller’s funded Base USDC key in the MCP host env (never commit it):

export X402_PRIVATE_KEY=0xYOUR_BASE_USDC_PRIVATE_KEY
# PRIVATE_KEY is also accepted
node src/index.js

Claude Desktop / Cursor-style config:

{
  "mcpServers": {
    "grindfree-agent-security": {
      "command": "node",
      "args": ["/absolute/path/to/grindfree-agent-security/mcp-server/src/index.js"],
      "env": {
        "X402_PRIVATE_KEY": "0xYOUR_KEY"
      }
    }
  }
}

MCP tools

• promptshield_screen / promptshield_clean
• crawlsafe_check
• toolguard_evaluate — your agent must enforce allow/review/deny before executing the tool; this API cannot stop a bypass
• commandguard_command / commandguard_sql — check shell commands and SQL before running them
• memoryguard_screen — check content before saving it to long-term memory
• wireshield_scan — check agent output before rendering/sending it
• docshield_scan — check a local file (path), base64 bytes, or HTML/Markdown for hidden instructions (max 3 MB)
• grindfree_discovery — unpaid 402 / discovery probe (no spend)

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HTTP snippets (no MCP)

• examples/typescript-x402-fetch.ts — official @x402/fetch + @x402/evm
• examples/python-x402.py — unpaid probes + paid hook
• examples/langchain-tool.py — LangChain-style wrappers

Unpaid challenge (no wallet):

curl -sS -D - -o /tmp/ps402.json -X POST https://promptshield.grindfree.net/v1/screen \
  -H 'content-type: application/json' \
  -d '{"content":"hi","format":"text"}'
# Expect HTTP 402 + PAYMENT-REQUIRED

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Honest limits

• Heuristic / policy layers — not a full security program.
• CrawlSafe is not malware, phishing, or legal/ToS advice.
• All guards are deterministic rule packs (no LLM), so they are fast and cheap but can miss novel phrasing; decisions are advisory and your code must enforce block/deny.
• DocShield parses structure and text; it does not OCR images or render pages, and legacy .doc/.xls/.ppt return 415 (not charged).
• ToolGuard returns a decision; the caller/adapter must enforce it before tool execution. Missing policy → review. Not an exfiltration guarantee.
• ToolGuard: always enforce allow|review|deny in your adapter before tool execution (the API cannot stop a bypass). GrindFree has confirmed funded settlement + HTTP 200 delivery on /v1/evaluate via a self-funded Base USDC test; still verify with your own wallet in production.

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License

MIT — see LICENSE.