Best card for a store or category

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

With no annotations provided, the description carries the full behavioral burden and does so well. It discloses what is included (base rates, rotating bonuses, built-in benefits), what is excluded (personal bank offers), and describes the richness of the output (honest rate, why, caveats like merchant-code traps, activation, ties). It could add whether the operation is read-only, but it is clearly a non-mutating query.

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 with zero filler. The core purpose is front-loaded, and the second sentence packs the output contract and scope limitations efficiently. Every clause adds value; no redundancy with the schema.

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?

Given six parameters including a nested object and no output schema, the description compensates well by explicitly stating what is returned (card, honest rate, why, caveats). The schema handles parameter documentation. Minor gaps—such as what happens when no card in the wallet earns anything—are not addressed, but the description covers the main call path thoroughly.

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 schema already documents all six parameters and their types/constraints. The description adds modest context by tying 'given cards' to the wallet parameter and 'today' to the date window, but it does not clarify semantics beyond what the schema provides. The baseline of 3 is appropriate.

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 purpose: determine which held card earns the most at a merchant or spend category as of a given date. It names the inputs (given cards), the output (card, rate, why, caveats), and clearly separates itself from sibling tools like search_cards by referencing cards 'from search_cards' and excluding personal bank offers.

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 implicitly routes usage: use this when you already have a wallet of cards and need the best earner for a store or category. It also discloses an important limitation (personal bank offers are not consulted), which helps an agent avoid over-promising. However, it does not explicitly name alternative tools (e.g., rotating_calendar for schedule lookups) or state when-not-to-use conditions.

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