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 covered. The description adds valuable behavioral context: it explicitly states the tool returns both answers rather than one, and explains the rationale ('the card the bureaus notice least is often not the card with the lowest rate'). This goes beyond the annotations and gives the agent insight into the output structure and logic.

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 three sentences, each earning its place: the first states the core purpose and outputs, the second explains the dual-answer behavior, and the third gives the usage trigger. It is front-loaded with the most important information and contains zero fluff.

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 the moderate complexity, the comprehensive schema (100% coverage), and the presence of an output schema (flagged as present), the description covers what an agent needs to invoke it correctly. It explains the dual-return behavior and the context for use. It does not go into detail about prerequisites or edge cases, but those are adequately handled by the schema and annotations.

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 input schema fully documents all three parameters with detailed descriptions (cards, amount, targetUtilization). The tool description adds no additional parameter semantics beyond what the schema already provides. The description does not clarify any subtle parameter interactions, but the schema is comprehensive, 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 (determine) and resource (which card for a purchase) and explicitly names the two answers it returns: least credit damage and lowest cost, plus the trade-off when they differ. This clearly distinguishes it from sibling tools like close_card_impact or next_move, which address different decisions.

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 gives an explicit trigger: 'Use it when someone asks which card to put something on.' This is a clear context for use. However, it does not explicitly mention alternatives or exclusions (e.g., when not to use it), though the sibling list implies other tools cover related but distinct scenarios.

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