Two integrations. One page.

For AI agents · call a tool

Every tool call is gated by x402. Hit the endpoint once, read the price tag, sign a USDC authorization, retry with the signature. Same request, two round trips.

Step 1. Call with no payment header. Get a 402 back carrying the exact amount, USDC address, seller wallet, and Arc network id.

curl -X POST https://keryxhq.xyz/api/call \
  -H "content-type: application/json" \
  -H "x-keryx-agent: my-agent" \
  -d '{
    "toolId": "solana.token-activity",
    "args": { "mintOrSymbol": "BONK" }
  }'
# → HTTP 402
# {
#   "x402Version": 1,
#   "error": "X-PAYMENT header is required",
#   "accepts": [{
#     "scheme": "exact",
#     "network": "eip155:5042002",
#     "asset": "0x3600000000000000000000000000000000000000",
#     "amount": "5000",
#     "payTo": "0x8F47…26B6",
#     "maxTimeoutSeconds": 60
#   }]
# }

Step 2. Sign an EIP-3009 USDC transferWithAuthorization against those requirements, base64-encode the signed payload, send it back in the X-PAYMENT header. The response carries the tool result, the settlement tx hash, and the ledger entry id in one shot.

curl -X POST https://keryxhq.xyz/api/call \
  -H "content-type: application/json" \
  -H "x-keryx-agent: my-agent" \
  -H "x-payment: $SIGNED_PAYLOAD_BASE64" \
  -d '{ "toolId": "solana.token-activity", "args": { "mintOrSymbol": "BONK" } }'
# → HTTP 200
# { "ok": true, "result": {...}, "settlement": { "mode": "gateway", "txHash": "0x…" } }

Discover tools first with GET /api/tools. Every listing includes the arg schema so an agent can plan calls without human help.

Agents that prefer a single front door can also hit /.well-known/x402 (JSON catalog of free + paid routes) or /llms.txt (plain-text map for LLM agents).

For publishers · list your endpoint

Use the publish form or POST directly. Your Arc wallet gets credited on every call, minus a 5% platform fee.

Seeded tools (Keryx runs the handler) are executable out of the box by /ask, MCP, and /api/call. Community tools are listed immediately. To make a published tool executable by Keryx today, provide a simple HTTPS POST endpoint that returns JSON (see publish form for exact contract).

curl -X POST https://keryxhq.xyz/api/publishers/tools \
  -H "content-type: application/json" \
  -d '{
    "id": "my.tool",
    "name": "My Tool",
    "summary": "Does one useful thing for agents.",
    "category": "utility",
    "priceUsd": 0.003,
    "publisherWallet": "0xYourArcWallet…",
    "publisherName": "You"
  }'

For Claude Code, Cursor, GitHub Copilot, and any MCP client

Real agents do not use our /ask chat. They talk directly to Keryx via the Model Context Protocol. Add the MCP server once and the agent gets the full catalog (20+ seeded tools + any community-published tools) as native tools.

Note on payments: Through MCP, tool calls are currently Keryx-sponsored (MCP clients do not yet send wallets). For autonomous paid calls, use POST /api/call with a buyer wallet — see /quickstart.ts and /quickstart.py. Free sample first: /api/demo. Production settles via the local Arc facilitator when a facilitator key is present (real Arcscan txs). Set CIRCLE_GATEWAY_PREFERRED=true + CIRCLE_GATEWAY_API_URL to force Circle Gateway; otherwise demo (synthetic hashes) on cold clones.

{
  "mcpServers": {
    "keryx": {
      "type": "http",
      "url": "https://keryxhq.xyz/api/mcp"
    }
  }
}

Cursor

Add the JSON block above to your Cursor settings (Tools & MCP) or project .cursor/mcp.json.
Or install the repo as a plugin: symlink to ~/.cursor/plugins/local/keryx or submit to the Cursor Marketplace.

Claude (Claude.ai, Claude Code, Claude Desktop)

Add as a custom connector:

• Go to Settings → Connectors (or "Add custom connector")
• Use the URL: https://keryxhq.xyz/api/mcp
• Paste the config block above if your client asks for it.

Note: The official Claude Connectors Directory requires a Team or Enterprise plan. With a Pro plan you can still add it manually using the URL.

GitHub Copilot (VS Code / Copilot CLI)

Add to .vscode/mcp.json (project) or your user MCP config:

{
  "servers": {
    "keryx": {
      "type": "http",
      "url": "https://keryxhq.xyz/api/mcp"
    }
  }
}

Or via CLI: copilot mcp add keryx --transport http --url https://keryxhq.xyz/api/mcp

One config. 20 real seeded tools + community-published tools. Direct calls (outside MCP) are paid per call in sub-cent USDC on Arc.

For publishers · integrate x402 yourself (SDKs planned)

First-party SDKs and an @keryx/* middleware are planned. Today you can implement the x402 flow directly (return 402 with price requirements, accept X-PAYMENT, settle via the same facilitator logic) or point a simple handlerUrl at your existing endpoint and let Keryx handle payment + forwarding.

See the whitepaper for the settlement modes and the publish form for the exact contract when providing a handlerUrl.