Developer API and MCP

Claude Code JSON config

{
  "mcpServers": {
    "fluxus": {
      "command": "npx",
      "args": ["fluxus-mcp"],
      "env": {
        "FLUXUS_BASE_URL": "https://your-domain.com",
        "FLUXUS_API_KEY": "your-bearer-token"
      }
    }
  }
}

Step 1 — get the challenge (runnable, no credentials needed)

curl -i -X POST https://fluxuspay.app/api/mpp/send \
  -H 'content-type: application/json' \
  -d '{"to":"0x000000000000000000000000000000000000aBcd","amount":"1.50","token":"pathUSD"}'

The server answers 402 Payment Required with the challenge in the WWW-Authenticate: Payment ... header and Cache-Control: no-store. The body describes what to pay:

HTTP/1.1 402 Payment Required
www-authenticate: Payment <challenge>
cache-control: no-store

{ "amount": "0.01", "currency": "pathUSD", "recipient": "0x..." }

Step 2 — pay and retry

A Credential must be signed by a Tempo account, so plain curl cannot produce one. Any MPP client can: the payment-aware fetch below settles the charge in pathUSD and replays the request with Authorization: Payment <credential>.

import { Mppx, tempo } from "mppx/client";
import { privateKeyToAccount } from "viem/accounts";

const mppx = Mppx.create({
  methods: [tempo({ account: privateKeyToAccount(process.env.AGENT_PRIVATE_KEY) })],
});

// mppx.fetch handles the 402 round-trip: challenge -> credential -> retry
const res = await mppx.fetch("https://fluxuspay.app/api/mpp/send", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({ to: "0xRecipient", amount: "1.50", token: "pathUSD" }),
});

console.log(res.status);                              // 200
console.log(res.headers.get("payment-receipt"));      // signed Receipt
console.log(await res.json());                        // { hash, explorerUrl, ... }

On success the response carries a signed Payment-Receipt header and Cache-Control: private. A replayed or tampered Credential is rejected with a fresh 402 rather than a 200.

Bearer alternative — /api/v1/send (fully runnable with curl)

curl -X POST https://fluxuspay.app/api/v1/send \
  -H "authorization: Bearer $FLUXUS_API_KEY" \
  -H 'content-type: application/json' \
  -d '{"to":"0xRecipient","amount":"1.50","token":"pathUSD","memo":"invoice-42"}'

# → {"amount":"1.50","amountUnits":"1500000","explorerUrl":"https://explore.tempo.xyz/tx/0x...",
#    "hash":"0x...","memo":"invoice-42","to":"0xRecipient","token":"pathUSD"}