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

Without annotations, the description carries the full burden. It discloses that the tool compares and ranks brands by cashback, perks, and savings, which is useful. However, it does not clarify whether any side effects occur (e.g., actually executing a purchase) or what the return format is. The word 'route_purchase' could ambiguously suggest transaction execution, but the description's language leans toward decision support only.

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 mostly concise and front-loaded, but the final sentence 'The core purchase intelligence tool for agentic commerce' is promotional and does not earn its place. The first two sentences convey the functional purpose effectively, but the third could be removed without loss.

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 tool with no output schema and no annotations, the description explains the high-level behavior (comparing and ranking) but fails to specify the exact return structure or whether it actually routes/purchases a product. It leaves some gaps for an agent, but the core purpose is clear enough.

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 schema already provides full descriptions for all four parameters, so baseline is 3. The tool description does not add meaningful semantic detail beyond the schema—it only echoes the concepts of intent and purchase amount. No additional context on parameter usage or syntax is provided.

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 explicitly states the tool finds the best brand to buy from based on cashback and rewards, then elaborates that it compares all matching brands and ranks them. This is a specific verb+resource+scope and distinguishes it from sibling comparison tools like compare_brands or compare_cashback.

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 gives a clear usage context: 'Given a shopping intent, compares all matching brands and ranks them.' This implies when to use the tool. However, it does not mention any exclusions or alternative tools, so it lacks explicit when-not-to-use guidance.

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