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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered; the description adds real behavior beyond that: the ~1,300-row pool size, the default sort and page size, and critically that live_total counts open auctions before filtering, which prevents misreading a filtered total. It does not disclose data freshness/latency or rate limits, which is why it is not a 5.

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?

Front-loaded with what the tool returns, then filters, sort, pagination and the live_total caveat — a logical order with no filler sentences. It is dense but somewhat redundant with the schema, since most parameter descriptions are repeated near-verbatim.

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 11 optional parameters, annotations, and an output schema present, the description covers the essentials: scope, filtering semantics, sort defaults, page bounds, and the meaning of live_total. It is complete enough to invoke correctly, with only freshness and cross-sibling routing left implicit.

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 documents all eleven parameters, and the description largely restates them (comma-separated ids, USD for max_bid, the 1/4/24/120/168 hour set, 10–50 per page). It adds only marginal value, mainly the live_total return-value note. A 3 is the correct baseline when the schema carries the parameter burden.

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?

States a specific verb and resource — list the auctions currently open on Bring a Trailer — plus the expected cardinality (~1,300) and the exact per-listing fields returned (current bid, end time, year, era, categories, country, premium/no-reserve). This clearly distinguishes it from bringatrailer_results (closed) and bringatrailer_listing (single record) without needing the 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?

The phrase 'currently open' plus the filter and sort menu makes the intended use case obvious, and it routes the agent to bringatrailer_filters as the source of category/era/country ids — a genuine cross-tool dependency. It does not explicitly state when to prefer a sibling such as bringatrailer_results or bringatrailer_makes instead, so there is no exclusion guidance.

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