x402 vs Skyfire vs Crossmint vs AgentKit — agent payment options compared
TL;DRx402 is an HTTP-level protocol — fifty lines of server code, no SDK on the agent side. Skyfire is a payment network with KYC and per-trip authorisations. Crossmint is a Web3 commerce SDK with cards plus stablecoins. Coinbase AgentKit is a wallet that ships an x402 client out of the box. Agents that need to buy disposable infrastructure (SMS, proxies, browsers) usually pick x402 because no party has to onboard the other.
TL;DR — pick by integration cost
If the merchant has not heard of you, x402 is the only option that does not require either side to sign up. The merchant returns 402, the agent signs and replays. Done.
If the agent's principal (the human or platform behind it) wants spending limits, audit logs, and centralised KYC, Skyfire fits. If the merchant wants to accept both cards and stablecoins through one SDK, Crossmint fits. If the agent runs on Coinbase infrastructure, AgentKit gives you a wallet plus an x402 client in one package.
Side-by-side feature matrix
| Feature | x402 | Skyfire | Crossmint | AgentKit |
|---|---|---|---|---|
| Layer | HTTP protocol | Payment network | Commerce SDK | Wallet + x402 client |
| Merchant integration | Implement /402 endpoint | Skyfire merchant API + KYB | Crossmint Storefront SDK | Implement /402 endpoint |
| Agent integration | Sign and replay | Skyfire agent API | Crossmint agent SDK | AgentKit SDK |
| Settlement | USDC + others | USDC + ACH/cards | USDC + cards | USDC on Base |
| Median latency | ~400ms | ~1.2s | ~2-30s (depends on rail) | ~400ms |
| Per-call fee | Network gas only | ~1-2% + base fee | ~2-3% on cards | Network gas only |
| Best fit | Disposable infra APIs | Mid-trip authorisation | Storefronts, NFTs, credits | Coinbase agent stacks |
| Open spec | Yes | Proprietary | Proprietary | Yes (uses x402) |
When x402 is the right answer
Pay-per-call APIs are the canonical x402 fit. If the resource is small, immediate, and the merchant has zero relationship with the buyer, x402 removes both sides' friction. Agent402 Stock prices captcha solves at $0.02 — there is no payment network that can profitably handle that with KYC and reconciliation overhead.
x402 is also the right answer when the merchant is open-source. Anyone can ship an x402 endpoint without signing a partner agreement. The protocol is permissionless on both ends.
When Skyfire or Crossmint is the right answer
Skyfire shines when the agent's principal needs strong controls — daily limits, allow-listed merchants, audit logs, dispute handling. Enterprise-grade agent deployments and procurement workflows fit Skyfire's model.
Crossmint is the natural pick for agents that buy in storefronts — NFT mints, in-game items, content credits — where the buyer wants to pay with a card and the seller wants stablecoin in their wallet. Crossmint mediates the rail conversion.
Can you stack them?
Yes. Agent402 Stock accepts payments signed by any wallet, including Skyfire's per-trip wallets and AgentKit wallets. The agent picks its rail; the merchant only needs to verify the on-chain settlement. Skyfire agents have already paid Agent402 Stock invoices in production.
Frequently asked
Which option has the lowest per-call cost?
x402 has the lowest per-call cost because the only fee is on-chain gas. Skyfire and Crossmint both add 1-3% network fees for the value-add services they provide.
Can my agent use multiple options simultaneously?
Yes. The agent decides per merchant. Most production agents we have observed use AgentKit (which speaks x402) for infrastructure consumables and Skyfire for agreements that need centralised limits.
Is Coinbase AgentKit required to use x402?
No. AgentKit is one of several wallets that can sign an x402 payload. Crossmint, Privy, and any EIP-712-capable wallet work equally well.