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

No annotations are provided, so the description carries full burden. It states that the tool compares unit prices and returns best buy, but does not disclose any potential side effects, permissions, or limitations. The description is adequate but not rich.

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 concise with 3 sentences covering purpose, usage, inputs/outputs, and a related tool. It is front-loaded and avoids unnecessary details.

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?

The tool is low complexity with one parameter and an output schema (not shown). The description mentions output ('price per unit and best buy'), so completeness is good. It also references a related tool, adding context.

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% for the single parameter 'items'. The description simplifies it as 'list of {price, quantity, unit}', adding minimal extra meaning. The description does not explain the parameter structure beyond what the schema already provides.

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 'Compare unit prices across packages to find the best deal' and specifies inputs and outputs. It distinguishes itself from siblings by mentioning a related tool (list_bundles) and by focusing on shopping price comparison.

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 says 'Use for shopping' which provides context, but lacks explicit when-not-to-use guidance or alternatives. It only references one sibling (list_bundles) for educational calculators, but does not cover when other similar calculators might be more appropriate.

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