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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds valuable behavioral context beyond these: it explains the format of d30Pct/d90Pct (percentages, null possibility for CardTrader) and the spoiler flag indicating pre-release cards that may change. These are meaningful data semantics that help the agent interpret results correctly, going beyond the annotation hints.

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?

The description is front-loaded with the core purpose and then lists the returned data types. It is detailed but each clause adds necessary information (e.g., price sources, percentage formats, spoiler caveat). It is not overly verbose relative to the complexity, though it could be slightly tightened by grouping related items. Overall it is well-structured and earns a high score.

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?

The tool is complex with many return fields and no output schema. The description compensates thoroughly by enumerating all major data categories, clarifying percentage semantics, noting the null case for d90Pct, and explaining the spoiler caveat. This gives the agent a complete picture of what to expect, making the description fully adequate for correct invocation and 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?

The schema description covers the single parameter cardNumber at 100% coverage with an example ('GD01-001'). The tool description does not add any extra parameter-specific details, so the baseline of 3 is appropriate. The description focuses on the return payload rather than the parameter.

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 clearly states the verb 'get' and the resource 'one card', then enumerates the specific data returned (stats, effect text, keywords, rulings, printings with prices, tournament play). This level of specificity makes it unambiguous that this tool retrieves comprehensive details for a single card, distinguishing it from siblings like search_cards or price_list without needing to name them.

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?

The description implies usage: when you have a specific card number and need full details. It provides clear context but does not explicitly mention when not to use it or name alternatives. Since it says 'Full details for one card', an agent can infer this is the tool for a single-card lookup, but there is no explicit routing guidance to alternatives like search_cards.

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