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

Annotations declare readOnlyHint=true and destructiveHint=false, so the tool is known to be safe and non-destructive. The description adds that it performs 'pure arithmetic' (no external calls), which is a key behavioral trait beyond annotations. However, it does not detail the output format (e.g., the exact wording of the verdict or whether it returns profit in addition to the verdict), leaving minor gaps for an agent.

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 two sentences of minimal length, with the core purpose front-loaded and the usage note (price_item) secondary. Every word earns its place without fluff. It is well-structured and easy to scan.

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 two-parameter tool with full schema coverage and annotations that signal safety, the description is nearly complete. It explains the tool's role and when to use it)Skip, but it does not specify the exact output schema or the verdict thresholds, which could be useful for agent planning. Since no output schema is provided, a bit more detail on the return format would push it to 5, but current completeness is strong.

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 fully documents both parameters ('cost' and 'expected_sale_price') with clear descriptions and ranges, achieving 100% coverage. The description adds no extra parameter-level detail beyond implying they correspond to 'what the user would pay' and 'expected sale price', which is redundant. The baseline for full coverage is 3, which 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's verb ('Net after eBay fees and a verdict') and resource ('for an expected sale price and what the user would pay'), making its purpose specific. It distinguishes itself from the sibling 'price_item' by explicitly noting this is 'pure arithmetic' and not for unknown sale prices, which helps differentiate it.

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 explicitly states when to use this tool: when both the expected sale price and the user's cost are known, and provides a direct alternative: 'use price_item first when the sale price is unknown.' This gives clear guidance on tool selection, which is absent in many definitions.

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