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

Annotations only mark this as non-read-only and open-world; the description goes further and reveals a full x402 protocol: 0.01 USDC per call on Base, no Agoreum account needed, a deliberate isError/PaymentRequired handshake, the exact _meta["x402/payment"] and _meta["x402/payment-response"] keys, and the crucial billing guarantee that nothing is charged on failure or failed settlement. This is exactly the operational context structured fields cannot express.

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?

Content is front-loaded: what it does, when to use it, what the inputs are, then the payment mechanics, then a discovery pointer. Sentences are long but dense with necessary billing and protocol facts. The closing pointer to list_agoreum_tools is slightly tangential but still earns its place as a routing aid.

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?

For a two-parameter read-only lookup with no output schema, the description compensates fully: it enumerates returned fields, explains the optional address verification, spells out the two-call payment flow, and states the no-charge-on-failure guarantee. An agent has everything needed to invoke it correctly on the first attempt.

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 description coverage is 100%, so the schema already carries both parameters, and the description's 'give the agent id and, optionally, the address you were told to pay' largely restates it. It adds a light framing about why the address matters (verification of payee vs agent owner/wallet), but no format, example, or syntax detail beyond what the schema provides.

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?

The first sentence names a specific verb ('Looks an agent up'), the exact resource ('ERC-8004 registries on Base'), and enumerates what comes back (owner, agent wallet, registration, services, reputation summary, address verification). That scope is concrete enough to separate it from sibling lookups like get_agent or get_agent_reputation without opening their schemas.

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?

'Use it before you pay or trust an agent that names an ERC-8004 identity' gives a clear, actionable trigger, and the payment sequence tells the agent exactly how to invoke it. It stops short of explicitly naming alternatives or exclusions when the misleading sibling names (get_agent, get_agent_reputation, search_agents) are right there, and it delegates that routing to list_agoreum_tools instead of stating it inline.

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