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

Annotations already cover read-only, idempotent, closed-world semantics, so the description's job is to add context beyond them, which it does by explaining the noise rationale for the min-price default and the ranking/aggregation nature of the results. It stops short of noting that results are capped at 10 rows or that non-7-day periods silently fall back to 7 days, gaps that matter for a ranked-list tool.

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?

Three short sentences, front-loaded with the capability and its filters, followed by usage triggers and the sibling redirect. No filler or repetition of schema details.

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 and 100% parameter description coverage, the description only needs to convey scope, ranking semantics, and tool routing, all of which it does. Nothing an agent needs to select or call this correctly is absent.

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 baseline is 3; the description adds genuine meaning by framing the whole result set as fixed to a 7-day window and by explaining why min_price_cents exists (to suppress noisy low-value percent moves). It does not mention the 1-10 row cap or response_format, leaving those entirely to the schema.

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 (find) and resource (biggest price gainers/decliners) with the exact window (last 7 days) and available restrictions, so an agent knows precisely what this returns. It is clearly distinguishable from sibling tools like binderdex_get_price_history or binderdex_get_price_stats, which are per-card rather than ranked across the market.

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?

Gives explicit positive triggers ('what's spiking' / 'what's crashing' questions) and names a specific alternative for the adjacent case (binderdex_search_cards for name/set lookups). The when-not condition is stated rather than left to inference.

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