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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description adds substantial behavioral context beyond that: it discloses the exact outputs (ratios, price per carat, differences, missing information) and the limitations (no verification, no ranking, no valuation, no best-diamond declaration). It also notes the currency constraint. This goes well beyond what annotations provide.

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?

Four sentences, each with distinct value: purpose, outputs, non-scope, and currency constraint. The most important information is front-loaded, and there is no filler or repetition of schema 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 description covers inputs, outputs, constraints, and limitations, which is strong for a tool with no output schema. It does not describe the precise output structure (e.g., whether results are per stone or aggregate), and it omits the role of the label, but these are minor gaps given the tool's simplicity and the absence of an output schema.

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 description coverage is 0%, so the description must compensate. It explains the core inputs (carat, measured millimeters, price, currency) and the count range (two to five). It does not explicitly mention the required 'label' field or map the millimeter properties to width_mm/length_mm by name, but it conveys the meaning of the key parameters, which is sufficient for an agent to understand how to populate the stones array.

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 opens with a specific verb and resource ('Compare two to five diamonds') and explicitly lists the data used (carat, measured millimeters, prices). It also names what it does NOT do (verify, rank, appraise, declare best), which clearly separates it from siblings like verify_diamond_report and lab_grown_price_index.

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 indicates when to use it (comparing supplied specs from any seller) and gives an explicit exclusion ('Never verifies specifications...'), implying it is not for verification or appraisal. It also sets a usage constraint (explicit currencies, no mixing). However, it does not name a specific alternative tool or condition like 'use verify_diamond_report for verification', so it is clear but not maximally explicit.

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