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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive). The description adds genuinely useful behavior: results are sorted most-expensive-first and each entry carries 30/90-day change and a Cardmarket price, which matters because there is no output schema.

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 leads with the core purpose and then layers scope and returned fields. Efficient, though packing three ideas into one sentence makes it slightly hard to parse.

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?

For a read-only listing tool with annotations covering safety, the description is largely self-sufficient and even compensates for the missing output schema by naming the returned fields. Only the limit parameter and default behavior remain unexplained.

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 50%: slug and source are documented, but limit and scope are not. The description partially compensates by explaining that slug accepts a set slug/code or rarity slug/code and by mapping the overall/set/rarity tiers to the scope concept, but it says nothing about limit or defaults.

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 resource (most valuable Gundam cards) and its scope axes (whole list, a set, or a rarity tier), with sort order made explicit. An agent understands what it returns, though it does not explicitly distinguish itself from siblings like market_movers or best_buys.

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?

Usage is implied by describing the three scope modes (overall/set/rarity), so an agent can infer how to query it. However there is no explicit when-to-use versus alternatives, no statement of when this beats market_movers, and no prerequisites noted.

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