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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds the mode-switching behavior of the result set, but this same behavior is restated in the parameter descriptions, so it contributes little genuinely new behavioral context (no pagination or trend-window disclosure).

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?

A single dense sentence that front-loads the primary purpose and then the mode branch. The em-dash-heavy construction is slightly awkward but every clause 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?

An output schema exists, so return values need no explanation, and the description covers both modes and their triggering condition. For a three-param, annotation-covered read tool this is essentially complete, with only the sibling boundary left implicit.

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 limit, subject, and category are already fully documented, including that subject overrides category. The description largely echoes the schema rather than adding format or syntax detail, so the baseline of 3 applies.

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?

Names the specific resource (card-market price-index movers) and clarifies the two modes it returns (cross-subject leaderboard vs. per-subject per-category breakdown). It is clearly distinct from news/asset siblings by the 'price-index movers' framing, but it never explicitly differentiates itself from alt_market_trends, which is the nearest sibling.

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 clear conditional context: use it for the leaderboard, or scope to a category, or set subject to get one entity's own trend. It does not, however, state when to prefer alt_market_trends or alt_card_search over this tool, so the agent must infer the boundary.

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