Protocols overview

Sly speaks six protocols that let AI agents transact with merchants, services, and each other. You integrate once, and the platform adapts to whichever protocol a counterparty uses.

Protocol	Origin	Best for	Typical flow
UCP	Sly-native	Merchant checkout, tokenized commerce, settlement rules	Merchant issues UCP token → agent exchanges for settlement
ACP	Stripe + OpenAI	Agentic checkout sessions with card networks	Agent opens checkout → completes payment → merchant confirms
AP2	Google	Pre-authorized spending mandates	Agent presents mandate → merchant executes within policy
x402	Coinbase	Micropayments for APIs (HTTP 402 revival)	API returns 402 → agent pays → retries with proof
MPP	Sly-native	Recurring M2M micropayments with session vouchers	Agent opens session + deposit → signs vouchers per call → closes
A2A	Google	Agent-to-agent task delegation and discovery	Agent A sends task to Agent B → gets deliverable → pays
MCP	Anthropic	Tool catalogs and resources for LLM agents	LLM discovers tools → invokes → receives results
Cards	Visa VIC + Mastercard Agent Pay	Card-rail transactions with network identity verification	Agent presents Web Bot Auth → vaulted card → network authorizes

How to pick

Most integrations use one or two protocols aligned to their partner ecosystem. Start here:

Selling on Stripe / OpenAI marketplaces → ACP
Selling on Google Cloud / Gemini ecosystem → AP2 and A2A
Monetizing APIs via one-off micropayments → x402
Monetizing APIs via recurring sessions with vouchers → MPP
Building a traditional checkout with agentic capabilities → UCP
Routing agent spend over card rails with Visa / Mastercard programs → Cards
Shipping Claude Desktop / agent tools → MCP

If in doubt, see the decision tree.

One SDK, all protocols

The @sly_ai/sdk exposes each protocol behind a dedicated client:

import { Sly } from '@sly_ai/sdk';
const sly = new Sly({ apiKey: process.env.SLY_API_KEY });

// Pick your protocol
await sly.ucp.createToken({...});
await sly.acp.createCheckout({...});
await sly.ap2.createMandate({...});
await sly.x402.pay({...});
await sly.a2a.sendTask({...});
await sly.mcp.listTools();

Composition

Protocols compose — you can issue a UCP token that settles on-chain via x402, or accept an AP2 mandate that executes through an ACP checkout. See /v1/composition and the composition guide for cross-protocol routing.

Discovery

Every protocol Sly supports is self-describing:

curl https://api.getsly.ai/v1/protocols

Returns the full list of enabled protocols for your tenant, their versions, and machine-readable capability specs. Agents can use this to negotiate at runtime.

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Protocols overview

How to pick

One SDK, all protocols

Composition

Discovery

​How to pick

​One SDK, all protocols

​Composition

​Discovery

How to pick

One SDK, all protocols

Composition

Discovery