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

Annotations already declare read-only, idempotent, closed-world behavior, so the description's added value is the substance it supplies: prices come from Dave's Auto Center retail, labor is excluded, and a field indicates whether each price is exact — implying some are estimates. The phrase 'every documented failure we can price' usefully signals that coverage is partial. It does not discuss missing-price handling or authorization, but the additions are meaningful beyond the annotations.

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?

One sentence with no filler, and the scope-plus-output information is front-loaded. The opening clause ('The parts budget of every documented failure we can price on one engine platform') is dense and reads as a garden path, but nothing is redundant.

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 single-parameter read tool with no output schema, the description covers the return shape, currency, price source, and labor exclusion — enough to call it correctly and interpret results. Minor gaps remain: behavior on an invalid platform id and what the record looks like for failures without a price.

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 single parameter is already documented as a 'Platform id from list_platforms'. The description adds only that the platform is an 'engine platform', which the schema effectively implies, so it neither compensates for nor extends the schema — baseline 3.

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 the resource precisely — repair costs for one engine platform — and spells out the returned fields (band, low/high USD, exactness flag). It does not use a clear verb such as 'list' and does not name the overlapping sibling get_failure_modes, but the scope is unambiguous enough to distinguish it from the other lookup tools.

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?

There is no when-to-use guidance and no alternative is named, even though get_failure_modes covers the same documented failures and is the obvious adjacent tool. The only usage-adjacent statements are constraints ('Parts only, no labor', 'one engine platform'), which narrow scope but do not tell an agent when to pick this tool over a sibling.

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