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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds useful behavioral context: it returns a winner and displays each items[].buy to the human. This goes beyond annotation data and does not contradict it.

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?

Two sentences, no fluff. The first sentence states purpose and outcome; the second clarifies the human-facing output. Every word earns its place.

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 simple with one parameter and no output schema. The description explains the returned winner and the buy-link display, but does not specify comparison criteria (e.g., price, rating), which could leave the agent uncertain about how the 'winner' is determined. Overall sufficient for a basic compare tool.

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 'ids' parameter. The description adds the critical constraint '2+' (at least two product IDs) and qualifies them as 'Agent Rails' product IDs, providing meaningful guidance beyond the schema's plain 'product ids'.

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 'Compare', a specific resource ('Agent Rails product ids'), and a concrete outcome ('return a winner'). This clearly distinguishes the tool from siblings like get_product, search_products, and make_buy_link.

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 clearly implies when to use the tool: when you have 2+ product IDs to compare. It does not explicitly mention alternatives or exclusions, but the context is unambiguous and the sibling tools have distinct purposes.

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