World Liberty Financial ($WLFI) has unveiled AgentPay SDK v0.2.1, an enhancement that expands its open-source AI agent payment toolkit to accommodate x402 and MPP (Machine Payment Protocol) HTTP payment workflows, while also broadening EIP-3009 signing support and introducing Tempo mainnet compatibility.
Introduction to AgentPay SDK
AgentPay SDK can be likened to a wallet and payment system designed specifically for AI agents, rather than humans.
During the execution of a task by an AI agent, there is often a need to make payments for various services: accessing a paid API, utilizing a service, or completing a machine-to-machine transaction. Without a dedicated payment layer, the agent may struggle to carry out the task or have to rely on an external system to manage the financial aspect.
AgentPay resolves this issue by providing the agent with its own wallet, a set of spending rules defined by the operator, and the capability to locally sign and transmit payments without involving $WLFI or any third party. The agent can spend within the limits set by the operator.
SDK stands for Software Development Kit, which comprises tools developers utilize to create or extend software. In this context, the kit includes a command-line interface (CLI), a local signing daemon, a policy engine, and a skill pack that connects the wallet to agent hosts like Claude Code, Codex, and OpenClaw.
Enhancements in AgentPay SDK v0.2.1
The initial AgentPay SDK, launched around March 21, provided AI agents with a local, self-custodial runtime for setting up wallets, executing policy-based transfers, and requiring human approval at checkpoints. Version 0.2.1 builds upon this foundation by enabling agents to make payments for API access and HTTP-native services directly, without relinquishing control to the operator.
All transactions are settled in $USD1, the dollar-pegged stablecoin of $WLFI, which reportedly has approximately $4.4 billion in circulation according to DefiLlama.
Features of x402 Support
The x402 flow manages HTTP 402 payment responses, a standard wherein an API indicates that payment is required before access is granted to a resource. With v0.2.1, AgentPay now supports:
- Exact-payment and EIP-3009 x402 HTTP payment flows
- Reusable controls for HTTP requests including –method, repeatable –header, –data, and –json-body
The workflow is as follows: the agent requests a resource, the API responds with a 402 status and a price, AgentPay verifies the operator’s spending policy, signs locally using EIP-3009, and retries with payment proof attached. Subsequently, the API delivers the data.
Features of MPP Support
MPP (Machine Payment Protocol) introduces session-based payments on Tempo mainnet. Instead of making individual payments for each request, an agent can initiate a session, deposit funds, execute multiple requests, and conclude the session once the task is completed.
New MPP functionalities in v0.2.1 include:
- MPP HTTP 402 payments on Tempo mainnet
- Tempo session workflows with session initiation, voucher signing, optional –deposit, automatic top-up, and explicit closure
- Persistent session reuse via –session-state-file
- Decoded Payment-Receipt output along with JSON and NDJSON automation modes
Maintaining Operator Control with AgentPay
This serves as the fundamental design principle that underpins the SDK. Every transaction, whether a simple transfer or a paid API interaction, undergoes scrutiny by the local policy engine before any signing occurs. There are no avenues that bypass policy enforcement.
The architecture comprises four layers: a command-line interface (CLI), a local signing daemon, a policy engine, and a skill pack for integration with agent hosts like Claude Code, Codex, and OpenClaw. The operator’s private keys remain local. $WLFI does not hold assets, access keys, or process funds.
If a transaction exceeds a predefined threshold, the SDK pauses and necessitates human approval. In cases where the wallet balance runs low, the system halts the operation and provides an error message containing the wallet address, chain ID, and a QR code for replenishment.
The SDK does not impose platform fees; only standard blockchain gas fees apply. It is distributed under the MIT license without telemetry or auto-update mechanisms.
Target Audience for AgentPay SDK v0.2.1
AgentPay caters to developers creating autonomous agents that require payment for services during execution, such as paid APIs, data feeds, or machine-to-machine services, while ensuring that a human operator retains control over the movement of funds. The setup, initially designed for macOS, integrates with macOS Keychain and operates a root-managed LaunchDaemon locally.
Concluding Remarks
AgentPay SDK v0.2.1 introduces a capability that was absent in the original release: enabling AI agents to make real-time payments during tasks without compromising the operator’s control over financial transactions.
With the inclusion of x402 and MPP support, agents can now access paid APIs, data feeds, and HTTP-native services seamlessly within their operational flow. Sessions can be initiated, funded, utilized across multiple requests, and concluded, all within the predefined policy boundaries set by the operator.
The core design principles remain unchanged. Keys and signing operations remain local. $WLFI has no access to wallets or funds. The extension lies in the enhanced capabilities that the agent can leverage within this controlled environment.
For developers creating autonomous agents that interact with paid services, v0.2.1 bridges a practical gap that was left open by the initial release.
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World LibertyFi on X: Post on March 31
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World LibertyFi docs: About AgentPay SDK
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Report by The Defiant: World Liberty Financial Launches Toolkit to Let AI Agents Spend $USD1
