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

With no annotations, the description carries the full burden. It clearly indicates this is a paid operation with a specific payment flow, something an agent must know before invoking. It also implies a read-only nature but doesn't explicitly state it; however, the payment requirement is a critical behavioral disclosure.

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?

The description is three sentences, front-loaded with the core purpose, then the cost and payment flow. It's efficient, but the payment flow explanation could be seen as slightly dense for a single sentence.

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 tool with one optional parameter and no output schema, the description covers the what, the when, and the how-to-pay. It lacks details on the output format, but since there's no output schema, this is a minor gap. The description is comprehensive for an agent to use it correctly.

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?

The schema has one parameter (payment) with 100% description coverage. The description adds significant context beyond the schema: it explains the payment parameter's role in the two-step flow, including the format (base64 payload) and how it completes the purchase. This enriches the schema's minimal description.

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 description clearly states the tool maps the agent economy on Arc by listing agents in the ERC-8004 registry, including owner, services, and x402 acceptance. It distinguishes itself from siblings like arc_agent_search and arc_agent_status by focusing on the registry-wide mapping, though it doesn't explicitly name a sibling.

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?

It explicitly explains the two-step payment flow: first call without payment to get terms, sign them, then call with payment. It also specifies the payment methods and cost, which is crucial for calling the tool correctly.

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