Identify a card from a photo

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is known. The description adds valuable context: the credit cost (25 vs 1) and the behavior that the tool 'says so when it cannot' identify. It also explains the inherent limitation of reprints sharing artwork. No contradiction with annotations, and the added behavioral detail goes beyond the structured 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?

Three sentences, each carrying weight: purpose, usage caution with rationale, and cost plus parameter hints. Front-loaded with the core action, no filler or redundant wording. Efficiently structured for an agent to parse quickly.

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 should convey what the tool returns—'ranked candidates' covers that. It also addresses cost, failure behavior, and optional parameter triggers. While it doesn't specify the exact candidate structure (e.g., card fields), that is likely inferable from the tool's purpose and sibling tools. Given the tool's simplicity and the annotations covering read-only, this is reasonably complete.

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 the baseline is 3. The description adds one piece of parameter guidance—'Pass set or region when the user has told you either'—which helps the agent decide when to supply optional params. This is a modest but real addition beyond the schema's own per-parameter descriptions.

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 opens with a specific verb and resource: 'Recognise a Pokemon card from a photograph and return ranked candidates.' It clearly distinguishes itself from sibling tools (search, prices, sets, etc.) by focusing on image-based identification, and it explicitly notes that reprints share artwork, so visual identification alone cannot name a printing—this differentiates it from a plain image-to-name lookup.

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?

It gives explicit when-to-use guidance: 'Use this instead of guessing from what you see in an image' and warns against looping with 'do not call it in a loop' due to credit cost. It also instructs when to pass optional parameters: 'Pass set or region when the user has told you either.' This is clear, actionable, and covers both usage and exclusions.

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