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

With no annotations, the description carries the full disclosure burden and does well: it states the exact price ($0.004 per call), the accepted payment rails (USDC on Arc, Base or Solana; XNT on X1), and that the purchase completes inside the call when a signed payload is supplied. It does not cover rate limits, pagination, or result size, but the core economic and transactional behavior is transparent.

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?

Three tight sentences: what the data is, what it costs, how to pay. The payment-flow instruction is front-loaded enough to be found immediately. The chain enumeration in parentheses is slightly dense but each item is load-bearing for an agent choosing a rail.

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 and only one optional parameter, the description sensibly doubles as a return-value summary by listing the fields each agent record carries. Combined with the payment mechanics, an agent has enough to call correctly. Pagination and result-volume behavior are the remaining gap for a registry-wide listing.

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% and the schema already explains the `payment` field as a base64 PAYMENT-SIGNATURE payload. The description adds the meaning that is not in the schema: that omitting it returns terms, and that supplying it completes the purchase in-call. That sequencing context is genuinely useful beyond the field definition.

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 uses a specific verb-and-resource framing: it enumerates agents in the ERC-8004 registry that publish a registration file, and names the fields returned (owner, services, x402 acceptance). That is far more concrete than a generic 'agent market' label. It stops short of explicitly distinguishing itself from nearby siblings such as arc_agent_search or market_search, so the boundary is inferred rather than stated.

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?

The two-step payment handshake is spelled out precisely: call once without `payment` to get terms, sign with your own wallet, call again with `payment`. That is actionable procedural guidance an agent can follow without guessing. What is missing is when to prefer this tool over the sibling search/reputation tools, so routing guidance is incomplete.

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