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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the description does not need to repeat safety traits. It adds value by revealing the output structure (comparison of price, rating, shipping, features) and the 'side by side' presentation. No contradiction with annotations, and it supplements them with expected output details.

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 consists of exactly two sentences: the first states the function and output, the second gives usage guidance. Every word is purposeful, with no redundancy or filler. It is front-loaded and immediately actionable.

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, the description doesn't need to detail return values. The description covers purpose, usage, and scope, while the annotations cover safety and openness. The tool's low complexity (single parameter) means this is fully complete for an agent to invoke correctly.

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% and the sole parameter 'products' is described in the schema itself with 'List of products to compare (2-5 items)'. The description mirrors this constraint but adds no new meaning about parameter composition (e.g., provider/product_id fields). Since the schema does the heavy lifting, 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 action (compare), the target (products), and the scope (2-5, side by side). It also specifies the comparison attributes (price, rating, shipping, key features), which distinguishes it from sibling tools like compare_offers (offer-level comparison) and find_lowest_price (price-only focus).

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 provides a clear usage context: 'Use when the user is deciding between options.' This tells the agent when to select this tool, but it does not explicitly mention when not to use it or name alternative tools. It's good context but lacks exclusions or explicit alternatives.

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