Protocols overview

Six agentic commerce protocols, one SDK. What each is for and when to use it.

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
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

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 micropayments → x402
• Building a traditional checkout with agentic capabilities → UCP
• 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.