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Edison Flores
Edison Flores

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MarketNow 3.0: Sentinel MCP Interceptor, x402 streaming payments, and agent skill stacks

#mcp #ai #agents #security

What is new

MarketNow just shipped 4 new features that bring it closer to the agent economy vision:

1. Sentinel MCP Interceptor (L3 Runtime Guardrail)

A real-time JSON-RPC interceptor that sits between your agent and the MCP server. It inspects every tools/call for policy violations BEFORE the call reaches the server.

5 policy rules:

  • Block reads of .env, .aws/credentials, .ssh/id_rsa
  • Block dangerous commands (rm -rf, DROP TABLE, mkfs)
  • Block unauthorized process spawns (exec, spawn, child_process)
  • Block system directory writes (/etc/, /root/, C:\\Windows)
  • Warn on non-allowlisted network calls

Try it: POST https://marketnow.site/api/interceptor with a JSON-RPC payload.

2. Streaming Metered Billing (x402)

Per-call micro-payments in USDC on Base. An agent opens a payment channel, then each tool call deducts $0.01 USDC. No human confirmation needed per call.

POST /api/stream { skill_id, wallet_address, calls: 10 }
→ channel_id: ch_xxx, calls_remaining: 10

GET /api/stream?channel_id=ch_xxx&call=1
→ call_number: 1, calls_remaining: 9, cost: $0.01
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3. Agent Skill Stacks (Portfolios)

Pre-configured kits for specific use cases. One command installs everything:

npx -y marketnow-install-stack financial-auditor
npx -y marketnow-install-stack growth-hacking
npx -y marketnow-install-stack dev-productivity
npx -y marketnow-install-stack security-analyst
npx -y marketnow-install-stack data-pipeline
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Each stack generates the claude_desktop_config.json snippet automatically.

4. A2A Remote Execution

Delegate a task to a remote agent that already has the skill installed. No local install needed.

POST /api/execute { skill_id, input, atc_card_id, mandate_id }
→ job_id: job_xxx, status: queued, cost: $0.01 USDC

GET /api/execute?job_id=job_xxx
→ status: completed, result: { ... }
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Security audit response

We also completed the security audit from Antigravity AI:

  • ATC issuance: now requires Ed25519 proof-of-ownership + rate limited (5/hour)
  • Sentinel certificates: migrated from SHA-256 hash to Ed25519 (RFC 8032) signatures
  • CORS: POST endpoints restricted to known origins
  • Honeypots: documented in HONEYPOTS.md, Gitleaks noise reduced
  • /api/search: was 404, now returns real results (25 results for discord)

Stats

  • 9,248 MCP skills in catalog (100% free)
  • 9,238 audited by Sentinel
  • 57 ATCs issued
  • 50 dev.to articles published
  • 12 API endpoints operational on Vercel Hobby
  • npm: marketnow-mcp (1,7.0) + marketnow-install-stack (1.0.0)

What is next

We are looking for:

  1. First paying seller — the marketplace is ready, we need sellers
  2. GitHub stars — help us reach 100: https://github.com/edgarfloresguerra2011-a11y/marketnow
  3. Community feedback — try the interceptor, streaming payments, or stacks and tell us what you think
  4. Partnerships — if you build MCP tools, we want to list them

The code is open source (proprietary license). The trust ledger (57 ATCs + 2 receipts) is publicly auditable.

Website: https://marketnow.site
npm: https://www.npmjs.com/package/marketnow-install-stack
GitHub: https://github.com/edgarfloresguerra2011-a11y/marketnow

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