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

Annotations already declare read-only, idempotent, non-destructive, closed-world, and the description is consistent with that. Beyond them it adds real behavioral detail: the call is free, wrong targets are still answered free of charge, and the price is derived from the endpoint's own listed prices rather than a global fee schedule.

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 definition front-loaded before the pricing mechanics and the HTTP equivalent. Dense but no wasted sentences; the 'HTTP equivalent' trailer is only modestly useful.

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 no output schema, the description does explain what the quote comprises (3-call plan plus per-test-call cost) and the free-on-failure guarantee, which is the main thing an agent needs to act on. Minor gaps remain around currency/units and whether the quote expires, but the essentials are 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?

Schema coverage is 100% and both parameters are self-documented, so the schema does the heavy lifting. The description's only added semantic is that pricing comes from the target endpoint's own listed prices when endpoint_path narrows the target, which is marginal over the schema text.

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 — a free cost quote for one verification run — and itemizes what the quote contains (the fixed 3-call plan plus summed constituent test-call prices). It does not explicitly contrast itself with arena_run or arena_eligible, so an agent must infer the quote/run/eligibility split rather than being told.

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?

'before payment' and 'answered free' imply this is the pre-run pricing step and that unknown/ineligible targets cost nothing, which is useful timing guidance. However, no sibling is named as the next or alternative step (arena_run, arena_result), so the workflow position is only implied.

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