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

With no annotations, the description carries the burden of explaining behavior, and it does so well by defining the matching logic: same year, product, card number, and subjects, but different set. It also gives a concrete example (base vs. refractor), which clarifies the intended semantics beyond the 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?

The description is a single, focused sentence with the core action front-loaded and the defining criteria placed immediately after the colon. It includes a useful example without unnecessary filler.

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 low-complexity, one-parameter tool with no output schema or annotations, the description is nearly complete: it states what the tool does, the precise variant criteria, and implies a list result. It could mention the return shape or empty-result behavior, but those are minor gaps given the simplicity.

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 single parameter card_id is already fully described in the schema ('The card_id of the card'), so schema coverage is 100%. The description adds no additional detail about the parameter's format, source, or constraints, which is acceptable given the baseline for high schema coverage.

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 uses a specific verb ('Find') and a clear resource ('parallels/variants of a card'), then precisely defines what counts as a variant by listing the matching attributes and the different-set condition. This distinguishes it from siblings like get_card or search_cards, which target a single card or broader searches.

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 clearly implies when to use the tool: when you already have a card_id and want to discover its parallels or variants. It does not explicitly name alternatives or exclusion criteria, but the context is specific enough for an agent to route correctly among the siblings.

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