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

Annotations already declare readOnly/idempotent/safe and closed-world, so the safety profile is covered. The description adds real context beyond that: corpus size (1.5M+), grading companies covered, the 10-result cap, and the highest-value-first ordering, which tells the agent how to interpret and trust results.

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?

Two sentences, zero filler, front-loaded with verb+resource and followed immediately by return shape and ordering. Every clause carries information an agent would otherwise have to guess.

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 no output schema, the description usefully discloses result count, ordering, and that each match carries a Slabline value — enough to decide whether the result is worth consuming. It stops short of naming other returned fields, but the essential return contract is present for a two-parameter lookup tool.

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 description coverage is 100%, so both parameters are already documented, and the description's 'up to 10 matches' merely restates the limit bound. It adds a little framing about what the query string should target, but nothing beyond the schema's own examples.

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 and resource ('Search Slabline's catalogue of graded cards') plus the searchable axes (player, set, year), which is clear. It does not distinguish itself from the sibling 'search' or 'value_card', so an agent must infer which entry point applies.

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 when this tool applies by naming the supported query dimensions (player, set, year), but never states when to prefer it over 'search' or 'value_card', nor any exclusions or prerequisites. Usage is inferable rather than specified.

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