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

Annotations already declare readOnlyHint and openWorldHint. The description adds real context beyond them: results are paginated, the response 'discovers categories and available price metrics,' and 'external price-display permission is not confirmed by this endpoint' warns that returned prices may not be displayable. That caveat is a meaningful behavioral 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?

Three sentences, front-loaded with the core purpose and the pagination caveat placed logically before the conditional detail. The phrase 'The response discovers categories and available price metrics' is slightly awkward but not wasteful.

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 readOnly annotations, a full schema, and an output schema, the description only needs to add orientation — which it does, including the price-display permission caveat. Complete enough to call correctly, though the sibling routing and the game_id/GameID naming gap remain minor holes.

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 baseline is 3. The description adds the conditional game_id presence/absence rule, but it uses 'game_id' while the schema field is 'GameID', and it says nothing about Kind, Limit, Offset, ProductID, or CategoryID that the schema already documents.

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+resource: 'Returns a paginated Cardmarket daily price-guide file for a game or global accessories.' This makes the scope clear and distinguishes file vs accessories mode. It doesn't explicitly differentiate from the sibling cardmarket_price_guide_categories, so it falls 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?

'Provide game_id for a game file and omit it for accessories' gives a concrete usage rule. However, it never says when to use this versus cardmarket_price_guide_categories or cardmarket_games, so alternative selection is left implied.

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