Overview

SplitStream is a pay-per-use layer on Circle's Arc L1. Anyone can list a service — a piece of content (article, song, photo) or a paid API — and get paid per use in USDC, with the payment split across every contributor on their own chain. Buyers can be humans or AI agents; agents pay per call via the x402 standard.

Core concepts

1. Get an API key

Open a publisher account once to get a scoped key (the demo key arc_test_sk_demo_0001 works out of the box).

curl -X POST localhost:8787/trpc/tenants.signup \
  -H 'content-type: application/json' \
  -d '{"name":"Acme Media","onchainAddress":"0xYourArcAddress0000000000000000000000000"}'
# → { apiKey: "arc_test_sk_...", ... }  (shown once)

2. List content (pay-per-piece, cross-chain split)

A reader pays a few cents to unlock; the price fans out to every contributor on their chain. Use the /publish form, or the API:

curl -X POST localhost:8787/api/v1/pieces \
  -H 'content-type: application/json' -H 'x-api-key: arc_test_sk_demo_0001' \
  -d '{
    "title": "The Stablecoin Frontier",
    "kind": "article",
    "priceUSDC": "0.05",
    "contributors": [
      { "role":"writer",       "address":"0x1111…", "targetChain":"base",     "splitBps":6000 },
      { "role":"editor",       "address":"0x2222…", "targetChain":"arbitrum", "splitBps":2500 },
      { "role":"photographer", "address":"0x3333…", "targetChain":"ethereum", "splitBps":1500 }
    ]
  }'

It's now live in the catalog and shareable at /piece/<id>.

3. List a paid API (x402 pay-per-call)

Register any HTTP endpoint with a per-call price. You integrate nothing — SplitStream becomes the x402 paywall and proxies the call on payment.

curl -X POST localhost:8787/api/v1/pieces \
  -H 'content-type: application/json' -H 'x-api-key: arc_test_sk_demo_0001' \
  -d '{
    "title": "My App: FX Rates",
    "kind": "api",
    "priceUSDC": "0.01",
    "endpoint": "https://api.yourapp.com/v1/fx?from=USD&to=EUR",
    "httpMethod": "GET",
    "contributors": [{ "role":"owner", "address":"0xYourArcEvmAddress", "targetChain":"base", "splitBps":10000 }]
  }'

Multi-owner APIs split automatically — list several contributors.

4. Authenticated APIs — access without KYC

If your endpoint needs a key, store it once with the piece. It's write-only — never returned by any read endpoint — and injected per call. The paying agent gets the result, never the key.

"auth": { "type":"bearer", "secret":"sk_live_…" }
"auth": { "type":"header", "name":"X-API-Key", "secret":"…" }
"auth": { "type":"query",  "name":"apikey",    "secret":"…" }

Reads expose only authenticated:true and authType — never the secret.

5. Getting paid — real USDC on Arc

A. Install in your AI (MCP)

Add SplitStream's hosted MCP server to any MCP client (Claude Code, Cursor, …) by URL — no clone, no install. Your AI then has tools to browse and pay for the live catalog; the user just talks normally.

claude mcp add --transport http splitstream https://splitstream-api-production.up.railway.app/mcp

Other clients (Cursor, Windsurf, …): add an HTTP/Streamable MCP server pointing at https://splitstream-api-production.up.railway.app/mcp.

Tools the agent gains: list_pieces, call_api, pay_for_piece (+ treasury tools).

Local dev alternative (needs the repo + Bun): claude mcp add splitstream -- bun run apps/server/src/mcp/stdio.ts

User:  "What's the USD→EUR rate right now?"
AI:    list_pieces → finds "FX Rate API"
       call_api(pieceId) → pays $0.01 → returns { "rates": { "EUR": 0.86 } }
AI:    "It's about €0.86 to the dollar."

B. x402 — any agent with a wallet

No SplitStream-specific install. An agent with an x402 client + a funded Arc wallet pays our endpoint the standard way. This is the same model the wider x402 ecosystem (incl. pay.sh) uses; Circle's pay-via-agent-wallet does exactly this on Arc.

# 1. request the resource — no payment yet
POST /api/v1/pieces/<id>/call
→ 402 Payment Required
  { "x402Version":1, "accepts":[{
      "scheme":"exact", "network":"arc-testnet",
      "maxAmountRequired":"10000", "payTo":"0x…", "asset":"0x3600000000000000000000000000000000000000",
      "nonce":"0x…", "resource":"/api/v1/pieces/<id>/call" }] }

# 2. pay maxAmountRequired USDC to payTo on Arc (your wallet signs it)

# 3. retry with the proof
POST /api/v1/pieces/<id>/call
   X-PAYMENT: base64({ x402Version:1, scheme:"exact", network:"arc-testnet",
                       payload:{ nonce:"0x…", from:"0xYou", authorization:"<txHash>" } })
→ 200 OK
  X-PAYMENT-RESPONSE: base64({ success:true, transaction:"0x…", payer:"0xYou" })
  { "paid":true, "mode":"live-arc", "payments":[…], "upstream":{ "ok":true, "body":{…} } }

Try the full handshake locally: pnpm --filter @arcane/server x402:call. The single-use nonce blocks replay.

C. REST / curl (content unlock or known API)

curl -X POST localhost:8787/api/v1/pieces/<id>/pay \
  -H 'content-type: application/json' -d '{"payer":"reader"}'
# → { unlock: { contributors:[ …paid per chain… ] } }

D. Storefront (human, one click)

Open the storefront: browse pieces, hit Unlock (content) or Pay & call (API), and see the cross-chain fan-out + live result. No account. To pay with your own wallet in real USDC, add Arc first (below).

E. Add Arc Testnet to your wallet

To pay with your own wallet you need Arc Testnet added — most wallets don't have it yet. One click adds it. On Arc, USDC is the gas token, so you only ever need USDC (no separate gas coin).

Endpoints

x402 wire format

Network & modes