💧 Spraay Canton

Batch payment infrastructure for Canton Network — UTXO-optimized batch transfers, MCP tooling for AI agents, and Canton Coin reward integration.

Spraay Canton brings Spraay Protocol's multi-chain batch payment orchestration to Canton Network, the privacy-enabled blockchain for regulated assets.

What It Does

Canton uses a UTXO model for token holdings (CIP-0056 Token Standard). Spraay Canton provides:

• Batch transfers — Send to N recipients in an optimized sequence of TransferFactory_Transfer commands
• UTXO management — Small-first selection strategy, dust consolidation, and merge delegation
• MCP tools — 5 tools for AI agent frameworks (LangChain, AutoGPT, CrewAI) to execute batch payments
• CC rewards — Automatic FeaturedAppActivityMarker creation for Canton Coin minting rewards
• REST API — Express server compatible with the Spraay gateway pattern

Architecture

┌─────────────────────────────────────────────────────┐
│                  AI Agents / Clients                  │
│          (MCP tools  |  REST API  |  Gateway)         │
└──────────────┬────────────────────┬──────────────────┘
               │                    │
       ┌───────▼───────┐    ┌──────▼──────┐
       │  MCP Server   │    │  Express API │
       │  (5 tools)    │    │  /api/v1/*   │
       └───────┬───────┘    └──────┬──────┘
               │                    │
         ┌─────▼────────────────────▼─────┐
         │      Batch Orchestrator         │
         │  • UTXO selection (small-first) │
         │  • Transfer construction        │
         │  • Activity marker creation     │
         └─────────────┬──────────────────┘
                       │
              ┌────────▼────────┐
              │  Canton Ledger  │
              │   Client        │
              │  (JSON API)     │
              └────────┬────────┘
                       │ HTTP/JSON
              ┌────────▼────────┐
              │  Canton Node    │
              │  (Participant)  │
              │  port 7575      │
              └─────────────────┘

Daml Model

The daml/Spraay/BatchPayment.daml module defines:

Contract	Purpose
SpraayServiceConfig	Operator settings (fee rate, max batch size)
BatchPaymentRequest	Submitted by sender, accepted by operator
BatchPaymentExecution	Active during batch processing
BatchPaymentReceipt	Immutable completion record (queryable via PQS)
SpraayActivityMarker	Drives Canton Coin reward minting

Quick Start

Prerequisites

• Node.js 18.20+
• DPM (curl -sSL https://get.digitalasset.com/install/install.sh | sh -s)
• Canton sandbox (included with DPM)

Setup

# Clone
git clone https://github.com/plagtech/spraay-canton.git
cd spraay-canton

# Install
npm install

# Build Daml model
dpm build

# Copy env
cp env.example .env

# Start Canton sandbox (background)
npm run sandbox &

# Generate TypeScript types from OpenAPI
npm run generate:api

# Start Spraay Canton
npm run dev

First Batch Payment

# 1. Allocate test parties
curl -X POST http://localhost:3100/api/v1/parties \
  -H "Content-Type: application/json" \
  -d '{"hint": "Alice"}'
# → {"party": "Alice::1220abc...", "isLocal": true}

curl -X POST http://localhost:3100/api/v1/parties \
  -H "Content-Type: application/json" \
  -d '{"hint": "Bob"}'

curl -X POST http://localhost:3100/api/v1/parties \
  -H "Content-Type: application/json" \
  -d '{"hint": "Carol"}'

# 2. Submit batch payment
curl -X POST http://localhost:3100/api/v1/batch \
  -H "Content-Type: application/json" \
  -d '{
    "senderPartyId": "Alice::1220abc...",
    "recipients": [
      {"partyId": "Bob::1220def...", "amount": 10.0, "memo": "Payment 1"},
      {"partyId": "Carol::1220ghi...", "amount": 5.0, "memo": "Payment 2"}
    ],
    "instrument": "CantonCoin"
  }'

# 3. Check holdings
curl http://localhost:3100/api/v1/holdings/Alice::1220abc...

MCP Integration

Smithery

{
  "name": "spraay-canton",
  "version": "0.1.0",
  "tools": [
    "canton_batch_payment",
    "canton_query_holdings",
    "canton_batch_status",
    "canton_allocate_party",
    "canton_health"
  ]
}

Claude Desktop

{
  "mcpServers": {
    "spraay-canton": {
      "command": "npx",
      "args": ["ts-node", "src/mcp/server.ts"],
      "env": {
        "CANTON_LEDGER_API_URL": "http://localhost:7575",
        "SPRAAY_OPERATOR_PARTY_ID": "your-operator-party-id"
      }
    }
  }
}

Canton Network Integration

Token Standard (CIP-0056)

Spraay Canton interacts with Canton's Token Standard interfaces:

• Holding (splice-api-token-holding-v1) — UTXO queries and balance checks
• TransferFactory (splice-api-token-transfer-instruction-v1) — Transfer execution
• TransferInstruction — Transfer acceptance and tracking

App Rewards

When deployed as a featured app on Canton Network, each successful batch generates a FeaturedAppActivityMarker that SV automation converts into AppRewardCoupon contracts for Canton Coin minting.

Self-featuring is available on DevNet for testing the reward flow.

Deployment Progression

1. LocalNet — dpm sandbox for development
2. DevNet — Self-featured, test reward flow
3. TestNet — GSF approval required
4. MainNet — Production deployment

Project Structure

spraay-canton/
├── daml/
│   └── Spraay/
│       └── BatchPayment.daml      # On-ledger contracts
├── src/
│   ├── api/
│   │   └── server.ts              # Express REST API
│   ├── batch/
│   │   ├── orchestrator.ts        # Batch execution engine
│   │   └── utxo-selection.ts      # UTXO selection strategy
│   ├── canton/
│   │   └── ledger-client.ts       # JSON Ledger API client
│   ├── mcp/
│   │   └── server.ts              # MCP tool server
│   ├── utils/
│   │   └── logger.ts
│   ├── config.ts                  # Environment configuration
│   └── index.ts                   # Main entry point
├── daml.yaml                      # Daml project config
├── package.json
├── tsconfig.json
└── env.example

Links

• Spraay Gateway — Main x402 gateway
• Canton Docs — Canton Network documentation
• CIP-0056 — Token Standard
• Canton Dev Fund — Grant proposals

License

0BSD — same as the Canton Quickstart.