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

Annotations only declare readOnlyHint=true, so the description carries most of the burden and does add value: it discloses the dedup rule, the default pricing unit (input tokens), and the shape of a returned row (price, where it is, card_url). It still says nothing about ordering guarantees beyond 'n cheapest' or about tie-breaking, but for a read-only lookup this is solid extra context.

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 compact sentences with the core behavior front-loaded and no filler. The parentheticals ('for a job (task)', '(input tokens by default)') make it slightly dense but each carries information.

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?

There is no output schema, and the description compensates by describing the returned row contents. With all parameters documented in the schema and read-only behavior implied by annotations, the definition covers what an agent needs to call it, though it could say more about ordering and edge cases like fewer than n models existing.

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 all four parameters are already fully documented, including enum meanings and defaults. The description only reinforces the default component ('input tokens by default') and the meaning of task, adding little beyond the schema, which is the expected baseline-3 situation.

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 verb+resource ('cheapest MODELS') scoped by a job/task, and adds a deduplication rule ('each model counted once at its own lowest current price') that separates it from a raw price listing. It does not explicitly differentiate itself from close siblings like cheapest, dearest_models, or cheapest_for_workload, so it falls short of a 5.

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 explicit when-to-use or when-not-to-use guidance, and no sibling is named as an alternative. The phrase 'for a job (task)' implies a task-based lookup scenario, but the reader must infer when to pick this over cheapest_for_workload or search_offers.

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