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

Beyond the readOnly/openWorld annotations, the description discloses the billing model ($0.002 USDC per successful call via x402 on Base, Solana or Arc), that failed calls are free, the ordering guarantee, and the upstream data source (BaT's public auctions page). Those are exactly the facts an agent needs before deciding to spend money on a call.

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?

Two sentences, front-loaded with what the tool returns before the pricing caveat. The first sentence is long and comma-chained, but every clause carries information an agent uses when selecting or calling the tool.

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 an output schema present, return-value structure need not be explained, and the annotations already carry the safety profile. The description still covers the cost model, ordering, filtering and provenance, leaving nothing material an agent would need before calling.

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 the schema already documents q, limit and noReserve including their examples and ranges. The description restates the same filtering semantics without adding format details the schema lacks, 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 names a specific resource (live Bring a Trailer auctions for collector cars, motorcycles and parts), enumerates the returned fields (title, model year, current bid with currency, auction end time, no-reserve flag, country, listing URL) and the sort order (soonest-ending first). That is enough to distinguish it from nearby siblings such as travel_autotrader or travel_ritchie_bros_auctioneers without opening any 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?

It explains both filters operationally – word matching in the title with a concrete example (porsche 911) and a no-reserve-only mode – so an agent knows how to narrow results. What is missing is an explicit statement of when to prefer this over the other vehicle-listing siblings, and no exclusions are given.

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