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Agents often need to pay for services—API calls, data access, compute—without a human approving each payment. HTTP 402 Payment Required is designed for this: when the agent calls a 402-protected API, the server returns payment requirements; the agent pays and retries; the server delivers the resource. Dynamic server wallets provide the signing and key management layer. The wire format and settlement depend on which protocol you use.

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Cross-chain funding via Fireblocks Flow

Agents often hold different tokens than what a paywall requires — ETH on Base when the API wants SOL, or USDC on Arbitrum when the payment must settle on Ethereum. Dynamic’s Fireblocks Flow API handles this automatically: it quotes a swap or bridge route, returns a signing payload, and settles funds to any target token on any chain. The complete closed loop uses the Flow API together with any Dynamic SDK for signing: 
POST /server/{envId}/flow/{mode} → POST /source → POST /quote
  → POST /prepare → SDK sign + broadcast on-chain → POST /broadcast → poll settlement
Any Dynamic SDK can be used for the signing step — Node, React, React Native, Flutter, Swift, Kotlin, or Unity. See docs.dynamic.xyz for your platform.
Fireblocks Flow requires feature enablement per-environment. If you see 400 "Flow is not enabled", request access below.

Request Flow Access

Email the Dynamic team with your environment ID to enable Fireblocks Flow.

Fireblocks Flow API guide

Full guide: flow creation, quote, signing (EVM + Solana), broadcast, and settlement polling.

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Reference implementation

dynamic-agent-payments is a working CLI and MCP server that pays both x402 and Tempo MPP APIs from a Dynamic server wallet. When the agent holds the wrong token or chain, it calls Fireblocks Flow to swap or bridge before signing. 
npx dynamic-agent-payments wallet
npx dynamic-agent-payments pay https://x402-api.fly.dev/api/price-feed
npx dynamic-agent-payments pay-mpp https://api.example.com/resource

dynamic-agent-payments on GitHub

CLI and MCP server for paying x402 and MPP APIs from a Dynamic server wallet, with cross-chain auto-funding via Fireblocks Flow.

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Build with x402

The x402 protocol defines how onchain payment is negotiated over HTTP. The client receives payment requirements in the 402 response, signs with its wallet, and retries the request with an X-Payment header. A facilitator (for example, the Fireblocks x402 facilitator) verifies and settles onchain. Best for: x402-protected APIs, zero-fee USDC payments on Base, Fireblocks facilitator.

Using Dynamic with x402

Wire up a Dynamic server wallet as the x402 payment client.

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Build with Tempo MPP

Tempo’s Machine Payment Protocol (MPP) extends HTTP 402 for machine-to-machine traffic. The mppx client handles negotiation, signing, and retry automatically. Dynamic’s Node SDK provides the MPC-backed signing account. Best for: APIs and services that target Tempo’s network, machine-to-machine payments on Tempo Moderato.

Machine Payments on Tempo (Node.js)

Create a Dynamic server wallet, fund it, and make MPP payments to 402-protected APIs.

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Choosing a protocol

If you’re building your own integration, x402 and Tempo MPP target different settlement layers:
x402Tempo MPP
Protocolx402MPP
SettlementOnchain (Base, USDC)Tempo network
Client libraryx402-fetch, x402-axiosmppx
FacilitatorFireblocks (and others)Tempo
For a full comparison and background on how 402 flows work, see the HTTP 402 overview.