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

Annotations already declare the tool read-only, idempotent, and not open-world. The description adds the key behavioral detail that discounts are applied sequentially ('in order'), which affects the result, and that both the final price and effective rate are returned. This adds useful behavioral context beyond 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?

The description is a single, concise sentence that is front-loaded with the core action and output. No redundant words or filler; every phrase contributes essential information.

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?

For a simple, pure calculation tool with two fully documented parameters, annotations for read-only/idempotent behavior, and an output schema (confirmed by context), the description fully covers the tool's purpose, inputs, and outputs. No critical information is missing.

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?

The input schema already covers both parameters with descriptions: 'price' as original price and 'discountsPct' as discounts in percent applied in order. The description reiterates these concepts but does not add new parameter-specific meaning. With 100% schema coverage, a 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 clearly states the tool computes the final price and effective single discount rate from stacked discounts applied in order. It uses a specific verb ('applied', 'final price') and distinctly differentiates from sibling tools like 'discount' or 'effective-rate' by focusing on successive discounts.

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 phrase 'Stacked discounts applied in order' implies when the tool is appropriate, but there is no explicit mention of when not to use it or how it compares to alternative tools like 'discount' for a single discount. Context is clear but no exclusions or alternatives are provided.

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