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

Annotations already provide readOnlyHint and openWorldHint, indicating the tool is safe and may produce varying results. The description adds important context: it explains that the tool returns a step-by-step skill for agents with wallets and a raw x402 endpoint, and it clarifies the decision logic for agents that cannot sign transactions. However, it does not detail any side effects or error conditions, but given the annotations, the added context is substantial.

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 a single, information-dense sentence followed by a clear directive. It front-loads the key selling point ('Free, no wallet needed') and packs in all critical details without redundancy. It could be improved by breaking into bullet points, but it is still well-structured for an agent to parse.

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?

The tool has an output schema (not shown here, but indicated), which likely details the return values, so the description doesn't need to. It clearly explains the purposeholistic behavior, including the conditional instructions for agents with/without wallets. The only minor gap is that it doesn't explain what to do if the listing is not for sale, but the description does say it returns whether it is for sale, so that is covered.

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 descriptions cover 100% of the parameters, defining `slug` and `owner` with examples. The description does not add further parameter-level detail beyond the schema, so the baseline 3 applies.

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's purpose: to provide buying information for a listing. It specifies the exact resources (listing status, version, price, page, skill, endpoint, server URL) it returns. It is distinct from siblings like `get_listing` and `purchase` by focusing on the 'how to buy' information rather than the action itself.

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 description explicitly tells the agent when to use this tool: if the user wants to buy without a wallet, answer with `without_a_wallet`; if the agent can sign transactions, follow `with_a_wallet` or call `purchase`. It also names the `purchase` tool as an alternative for those who can sign, providing clear guidance on usage.

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