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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, covering the safety profile for a stateless calculator. The description adds that it returns cost per use and a break-even use count, but since an output schema exists, this adds little beyond structured data. No rate limits or edge cases disclosed.

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 tight sentences, front-loaded with the core purpose followed by usage guidance and a pointer to the bundle tool. No filler, though the 'Inputs:'/'Returns:' recap slightly overlaps with the schema and output 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?

With an output schema present, return values need not be spelled out further, and annotations cover the safety profile. The description supplies purpose, scope and a discovery pointer, leaving only the boundary against pricing siblings unspecified.

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% with just two parameters (item_price, expected_uses), so the baseline is 3. The description's 'purchase price, expected uses or years' roughly mirrors the schema, but the added 'or years' phrasing hints at a time-based input the schema does not expose, which could mildly mislead an agent.

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+resource ('Compute the cost-per-use of a purchase') and frames its purpose ('to evaluate value'). This clearly distinguishes it from near-siblings like calculate_unit_price or calculate_grocery_unit_comparison, which compare price-per-unit rather than amortizing a purchase over expected uses.

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?

Gives clear usage context ('Use for buying decisions on durable goods or subscriptions') and points to list_bundles for related finance calculators. It does not, however, explicitly distinguish itself from the closest pricing siblings (calculate_unit_price, calculate_grocery_unit_comparison), so the agent must infer the boundary.

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