ERC-8004 Agent Instructions

What is ERC-8004 signing

ERC-8004 lets an AI agent cryptographically sign content using its on-chain wallet, producing a verifiable signature block that anyone can check against the agent's identity on Arbitrum.

Tool interface

The signing tool is called sign_content.

• Input: Raw content text only. No labels, no commentary, no formatting, no preamble. Strip everything that is not the actual message text before passing it.
• Output: A copy-paste ready block containing the original content followed by a compact signature footer.

Output format

The tool returns a string in exactly this structure:

[content]

---
Signed by [AgentName] ([fullId])
sig: 0x...
hash: 0x...
ts: [ISO 8601 timestamp]
Verify: [URL]

Example:

Hello, this is a signed message.

---
Signed by Keystone (eip155:42161:0x8004...a432:5)
sig: 0xf13bd8a9...
hash: 0x57caa12b...
ts: 2026-02-06T14:32:15.000Z
Verify: https://erc8004.orbiter.website/#eyJzIjoiMHg...

The fullId follows the format eip155:[chainId]:[registryAddress]:[agentId].

Display rules

• Present the entire output as a single code block.
• Do not add any preamble, commentary, or explanation before or after the signed block.
• Do not modify, reformat, or truncate any part of the signature footer.
• The verify link must remain intact and clickable.

Verification URL format

The verify URL is https://erc8004.orbiter.website/#[base64] where the fragment is a base64-encoded JSON object with these fields:

{
  "s": "0x...",   // signature
  "h": "0x...",   // content hash
  "a": "eip155:42161:0x...:5",  // agent full ID
  "n": "Keystone",              // agent name
  "t": "2026-02-06T14:32:15.000Z",  // timestamp (ISO 8601)
  "d": "First line of content"       // subject (first line, max 80 chars)
}

The d field is the first line of the signed content, truncated to 80 characters (cut at 77 + "..." if longer).

How verification works

• The content hash binds both the content and timestamp: keccak256(abi.encode(keccak256(content), timestamp)).
• The verifier recovers the signer address from the ECDSA signature (EIP-191 personal sign over the content hash).
• It then checks the recovered address against the agent's registered wallet on the Arbitrum identity registry.
• Everything runs client-side in the browser. No data is sent to any server.