Financial world freedom ($WLFI) has issued AgentPay SDK v0.2.1, an update that extends the open-source AI agent payment toolkit to support x402 and MPP (Machine Payment Protocol) HTTP payment flows, while also expanding support for EIP-3009 signing and adding Tempo mainnet compatibility.
What is AgentPay SDK?
Think of AgentPay SDK as a wallet and payment system built specifically for AI agents, not humans.
When an AI agent performs a task, it often needs to pay along the way: retrieving data from a paid API, accessing a service, or completing a machine-to-machine transaction. Without a purpose-built payment layer, that agent can’t do the work or must hand over control to a third-party system to process the money.
AgentPay solves that. It gives the agent their own wallet, a set of spending rules defined by the operator, and the ability to sign and send payments locally without having to contact $WLFI or a third party. The agent can spend money, but only within the limits set by the operator.
SDK stands for Software Development Kit, which is essentially a suite of tools that developers use to build or extend software. In this case, the kit includes a command-line interface (CLI), a local signing daemon, a policy engine, and a skillset that connects the wallet to agent hosts such as Claude Code, Codex, and OpenClaw.
What changed in AgentPay SDK v0.2.1?
The original AgentPay SDKreleased around March 21, gave AI agents a local, self-perpetuating runtime for setting up wallets, policy-based transfers, and human approval checkpoints. Version 0.2.1 builds on that foundation by allowing agents to pay directly for API access and HTTP-native services, without relinquishing control to the operator.
All transactions are processed $USD1, $WLFI‘is dollar-pegged stable currencyof which, according to DefiLlama, approximately $4.4 billion is in circulation.
Which adds x402 support
The x402 flow handles HTTP 402 payment responses, a standard where an API indicates that a resource requires payment before granting access. With v0.2.1, AgentPay supports:
- Exact payment and EIP-3009 x402 HTTP payment flows
- Reusable HTTP request checks included –methodrepeatable –header, –factsAnd –json body
The flow works like this: the agent requests a resource, the API responds with a 402 status and a price, AgentPay checks the operator’s spending policy, signs locally using EIP-3009, and tries again with the payment receipt attached. The API then returns the data.
Which adds MPP support
MPP (Machine Payment Protocol) introduces session-based payments to the Tempo mainnet. Instead of paying per request, an agent can open a session, deposit money, make multiple requests, and close when the job is done.
New MPP features in v0.2.1 include:
- MPP HTTP 402 payments on Tempo mainnet
- Tempo session expires with opened session, signing of voucher, optional –borgautomatic top-up and explicit shutdown
- Persistent reuse of sessions via –session-state-file
- Decoded output of payment receipts plus JSON and NDJSON automation modes
How does AgentPay keep operator control intact?
This is the core design question around which the SDK is built. Every transaction, whether a simple transfer or a paid API call, goes through the same local policy engine before any signing takes place. There is no code path that bypasses policy enforcement.
The architecture includes four layers: a command-line interface (CLI), a local signing daemon, a policy engine, and a skillset for integration with agent hosts such as Claude Code, Codex, and OpenClaw. Private keys never leave the operator’s machine. $WLFI does not store assets, access keys or handle money.
When a transaction exceeds a preset threshold, the SDK pauses and requires human approval. When a wallet is low on balance, the system stops operation and returns an error message with the wallet address, chain ID, and a QR code for replenishment.
The SDK does not charge any platform fees. Only standard blockchain gas fees apply. It is released under the MIT License without telemetry or automatic update mechanisms.
Who is AgentPay SDK v0.2.1 for?
AgentPay targets developers building autonomous agents that require payment at runtime for services, such as paid APIs, data feeds, or machine-to-machine services, while a human operator maintains control over how and when money moves. The macOS initial setup integrates with macOS Keychain and runs a root-managed LaunchDaemon locally.
Conclusion
AgentPay SDK v0.2.1 does something the original release couldn’t: it lets AI agents pay for work in real time, mid-task, without the operator losing control over how that money moves.
The addition of x402 and MPP support means agents can now access paid APIs, data feeds, and HTTP native services as part of their normal execution flow. Sessions can be opened, funded, used for multiple requests, and closed, all within the policy limits predefined by the operator.
The core design has not changed. Keys remain local. Signing remains local. $WLFI has no access to wallets or funds. The only thing that has been expanded is what the agent can do within that controlled environment.
For developers building autonomous agents that interact with paid services, v0.2.1 closes a practical hole left open by the first release.
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World LibertyFi on X: Posted on March 31
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World LibertyFi documents: About AgentPay SDK
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Report from The Defiant: World Liberty Financial launches toolkit to let AI agents spend money $USD1