How to Enable AI Agents to Call APIs, Purchase Permissions, and Complete Payments? Exploring ERC-8257.

Original Author: Shirley Li, Researcher at Web3Caff Research

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Compared to human users, the biggest advantage of an AI Agent is that, ideally, it possesses stronger autonomous execution capabilities: it can complete tasks by itself, execute operations automatically, and proactively call external tools without continuous human intervention. However, in the actual process of AI Agents calling tools (e.g., trading platform APIs, data analysis tools, oracles), they still face some issues.

Firstly, the access points for these tools are scattered across GitHub, official websites, centralized API platforms, etc., lacking a unified discovery channel. It is difficult for an AI Agent to independently locate and integrate the required tools without human intervention. Moreover, the specific payment methods on different platforms vary, lacking standardized processes. This creates certain difficulties for AI Agents in the tool-calling process.

Secondly, in the traditional internet environment, using an API typically requires developers to register an account, obtain an API Key, and perform permission verification according to specific rules. This process was originally designed for human participants. However, for an AI Agent to automatically complete registration, obtain credentials, and call tools, there is currently a lack of public and standardized implementation schemes.

Although the x402 protocol currently supports AI Agents in automatically completing payments, it is mainly suitable for "pay-per-use" open interfaces and struggles with more complex permission scenarios, such as users needing a subscription to access the service, or holding specific credentials to enjoy discounts.

To fill this gap, OpenSea recently attempted to introduce the ERC-8257 standard draft, aiming to establish an open, permissionless on-chain tool directory for AI Agents. This would allow AI Agents to autonomously discover tools, understand access rules, and automatically complete calling and payment once conditions are met.

In simple terms, the core of ERC-8257 is an on-chain tool registry. This registry is essentially a smart contract where tool developers can register information about their tools and access permissions on-chain, making them publicly available across the entire network.

However, since directly storing all data on-chain can be costly, ERC-8257 allows developers to store more detailed tool information on their own maintained servers or domains, presented in JSON format files (Manifest). The on-chain registry only records the link to these files. These off-chain files typically include: tool name, function description, API interface, calling method, pricing information, payment protocol, access rules, etc. The on-chain registry needs to record key data such as the address of the off-chain file, the file hash, and the developer's information. This design aims to prevent developers from privately tampering with the tool content later. When an AI Agent calls a tool, it can verify whether the off-chain content matches the information registered on-chain by checking the file hash.

Another crucial design in ERC-8257 is that access permissions are not fixed in format but are defined through independent smart contracts. Tool developers can freely define these contracts to specify who is eligible to call their tools. For example, developers can check if an AI Agent holds a specific NFT, holds a specific Token, has a subscription, or is on a specific whitelist, etc.

Consider an example: an on-chain analysis tool stipulates that the fee for a regular user to call the regular API is $0.05 per call, while a user holding a specific NFT only needs to pay $0.01 per call. Furthermore, if a user subscribes to the service (paying continuously via a designated Token or payment protocol), they can also gain access to premium analysis interfaces.

In this scenario, "holding a specific NFT" and "subscribing to the service" are two special types of access credentials. If the AI Agent currently lacks the corresponding permissions, it can obtain these prerequisites on-chain or in the marketplace (e.g., buying the NFT or completing the subscription) and then reapply for access.

However, it's important to note that when access permissions exist in the form of assets like NFTs or Tokens, they can enter the market circulation system. Consequently, they become subject to supply and demand dynamics, potentially leading to high value volatility or speculative behavior.

Therefore, ERC-8257 does not restrict the permission system to a single asset model. Instead, it chooses to remain open. Tool or service developers can select different access mechanisms based on specific needs, such as introducing non-transferable Soulbound NFTs to avoid value fluctuations caused by trading activities, or introducing non-asset-based mechanisms like reputation scores to reduce the impact of speculation.

On the payment side, ERC-8257 is also not responsible for defining specific payment logic. It only requires developers to declare in the JSON file which payment protocol they support, such as x402, on-chain ERC-20 payments, or other machine payment protocols. The actual payment execution will be handled by the corresponding protocol.

Looking at the overall workflow, ERC-8257 operates roughly as follows:

• A tool developer deploys the tool service, writes the corresponding access permissions, and submits the relevant information to the on-chain registry.
• When an AI Agent needs to call a specific tool or service, it can scan the on-chain registry. If it finds a suitable tool or service, it can further read the detailed description file to understand the calling rules.
• If the AI Agent does not meet the access conditions, it can attempt to acquire the necessary permissions and then initiate the call again.
• Finally, the AI Agent can autonomously complete the entire process of tool discovery, permission verification, payment, and calling without human intervention.

Source: The App Store for Agent Tools: ERC-8257

Overall, what ERC-8257 attempts to solve is not just the issue of how to put APIs on-chain, but how AI Agents can, like human users, automatically discover tools, understand access rules, obtain access permissions, and call these tools in a standardized way. From a design perspective, ERC-8257 will form a complementary relationship with the x402 protocol:

• ERC-8257 is expected to enable AI Agents to discover tools globally and determine whether they have access based on the rules.
• The x402 protocol handles payment and settlement during the tool-calling process. After a tool is permitted for use, it supports AI Agents paying on a per-call or per-frequency basis.

However, besides the aforementioned risk of value volatility and speculation if access permissions exist as assets like NFTs or Tokens, the actual implementation of the ERC-8257 standard will also face other potential risks and challenges.

For instance, although ERC-8257 provides a standardized framework for tool registration and access, different developers may still have variations in setting access conditions. While AI Agents can rely on a unified on-chain index path for tool discovery, they still need to adapt to different permission judgment logics during the actual calling process, introducing certain technical complexities.

Furthermore, regarding the trust mechanism, AI Agents currently compare the hash recorded on-chain with the off-chain tool description file to verify if the file has been tampered with during transmission. However, this mechanism only addresses the issue of data consistency. It cannot further guarantee whether the tool's operational logic is correct, whether its interface is trustworthy, or whether there are potential risks like information leakage during data processing. Additionally, since tool services are typically deployed on off-chain infrastructure, their long-term availability and stability still depend on the developer's operational capabilities. This means AI Agents also need to rely on external reputation mechanisms for selection.

It is evident that before the ERC-8257 standard is practically applied, aspects such as tool credibility and consistency of permission rules still require further verification and improvement.

Key Structure Diagram:

References:

[1] The App Store for Agent Tools: ERC-8257

[2] ERC-8257: Agent Tool Registry

Disclaimer

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