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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds genuinely new behavioral facts: prices are EUR as shown in the ValoTCG app, omissions mean 'every edition and language', and the call costs 3 credits — a real operational constraint an agent cannot get from structured fields.

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 front-loads the resource and ranking criterion, then the optional narrowing dimensions, then the cost. Nothing is wasted and no sentence merely restates the title.

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 ranked-list tool with 6 params and no output schema, the description supplies the currency, the filter defaults, and the credit cost — enough to call correctly. It stops short of describing what each returned item contains or how ties/ordering are handled, which would matter for result interpretation.

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 83% so the baseline is 3, and the description earns the extra point by clarifying the default semantics of the optional filters — an omitted edition_id means all editions, an omitted language means all languages, and product_type only applies when kind=sealed. The limit parameter is left unexplained but the schema covers it.

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?

The description names a specific resource and ranking criterion — 'Most valuable cards or sealed products of a game, by the price the ValoTCG app shows (EUR)' — which clearly separates it from retrieval tools like get_card or filtering tools like search_cards. It does not explicitly name a sibling alternative, which keeps it short of a 5.

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 the framing: use this when you want a ranked top-N by value, optionally narrowed to one edition, language, or sealed product type. There is no explicit exclusion or routing against near-neighbours such as top_movers (movement-based) or price_summary (aggregate statistics), 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.