Look up an agent (ERC-8004)

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint and openWorldHint, and the description goes well beyond them: it discloses that nothing is fetched off-chain, that registration is permissionless, and that being registered is not evidence of safety. This is exactly the kind of adversarial-context caveat an agent needs before treating the result as a trust signal.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads the core action, then the return fields, then the comparison behavior, then the safety caveat. The enumerated return list is long but every item earns its place given there is no output schema. Slightly dense, but no filler sentences.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description fully enumerates the returned fields (registered, owner, wallet, token_uri, uri_domain, declared_name, feedback_clients) plus the conditional comparison outputs. For a read-only lookup with three parameters, nothing an agent needs to call or interpret it is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3, but the description adds real semantics: agent_id is the number in the Identity Registry, and pay_to/resource exist specifically to produce address and domain comparisons. That comparison behavior is not derivable from the terse schema property descriptions alone.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource: reads an agent's ERC-8004 record from the on-chain registry on the active network. It immediately scopes what the tool does not reach ("the wallet never fetches the agent's website"), which separates it cleanly from the payment/wallet siblings. An agent can tell what this returns without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives concrete invocation guidance (supply agent_id; optionally pass pay_to and/or resource to trigger a comparison) and states the condition under which the result is trustworthy (mismatch only matters when the agent number came from a source you trust). No sibling alternative is named, but the siblings are unrelated domains so the omission is minor. Clear context without explicit when-not-to-call routing.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.