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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower, yet the description adds real methodology: the 50% gem-rate assumption, the requirement that both PSA 9 and PSA 10 prices exist to exclude thin-market outliers, and the default $25 fee. It stops short of describing result size or how the limit interacts with ranking, but the substantive behavioral disclosure is strong.

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?

Four tightly packed sentences with the primary trigger front-loaded and zero filler. Dense but every clause carries information; only minor cost is that the methodology clause sits mid-paragraph rather than being separated for scanability.

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?

An output schema exists, so return-value documentation is unnecessary, and the description still notes it returns card ids for grading_roi. Combined with the annotations, the trigger, the exclusion, and the ranking methodology, an agent has everything required to select and call this tool correctly.

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 75%, so parameter docs do most of the work, but the description still adds meaning: the fee is framed as an assumption used inside the profit formula (not just a number), and the both-prices requirement explains why some cards are silently absent. The 'limit' parameter and the exact gem-rate composition are not explained beyond 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 and resource ('ranks priced cards by expected net profit'), names the exact ranking criterion (50% gem rate, half PSA 10/half PSA 9, minus raw and fee), and explicitly carves out the sibling use case ('Do not use for a single named card'). An agent can distinguish it from grading_roi, search_cards, and get_card_prices without opening any 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?

Opens with an explicit trigger ('Use this when the user asks which cards in a game, sport or set have the biggest payoff from grading'), states the exclusion ('Do not use for a single named card'), and names the downstream tool ('Returns card ids for grading_roi'). When-to-use, when-not, and the alternative path are all present.

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