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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description adds genuinely new behavior: result count and ordering, per-photo scan billing, no charge on refused photos or errors, and in-memory processing with no retention. The privacy and cost disclosures are high-value context an agent cannot derive from the annotations.

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 compact sentences, front-loaded with purpose and result shape, followed by the chaining hint and then the cost/privacy clauses. Every clause carries information an agent would otherwise not have; there is no 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?

With no output schema, the description compensates by describing the return ('up to 5 Valo.Data cards, best first'), which is enough to parse results. It could say slightly more about what a candidate entry contains or what happens when no card is recognised, but the essentials for correct invocation are present.

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 game, image and language are already fully documented with constraints (base64/data URL, formats, 8 MB, 480 px minimum, language filter). The description adds no parameter-level meaning beyond that, so the baseline 3 applies.

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 states a specific verb and resource ('Recognise the card in a photo') and names the underlying engine (Valo.Vision), plus the result shape: up to 5 Valo.Data cards, best first. It does not distinguish itself from the sibling identify_card, which appears to cover similar ground, so an agent still has to guess between 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?

It gives clear next-step workflow guidance ('chain with price_summary for its price') and an explicit cost/retry rule ('1 scan per analysed photo; a refused photo or an error costs nothing'), which is exactly what an agent needs before attempting a call. It lacks an explicit when-to-use-this-instead-of-identify_card statement, so the guidance is contextual rather than exclusionary.

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