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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering safety and side-effect-free behavior. The description adds value beyond this by specifying the output style: a 'plain verdict' on hardness and a 'note on toughness', plus the side-by-side layout. This informs the agent about the nature of the result without contradicting annotations.

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, front-loaded with the core purpose and outcome, and includes a relevant example. No filler or redundancy—every sentence contributes to understanding the tool's function and typical use.

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?

Given the tool has an output schema (not provided in detail) and only two simple parameters, the description covers the essential aspects: what it does, the type of output (verdict, toughness note), and a use case. It does not mention error handling or edge cases (e.g., invalid gem names), but these are not critical for a read-only comparison tool with an output schema. The description is sufficiently complete for an agent to call it 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 description coverage is 0%, so the description must compensate. It says 'two gem species' and gives an example with 'sapphire or diamond', implying the parameters are gem names. However, it does not specify acceptable formats (e.g., common names vs. chemical formulas) or any validation requirements. For simple string parameters, this is a minor gap, but the description could be more explicit about what gem_a and gem_b should contain.

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 compares two gem species side-by-side, with a specific verb ('compare') and resource ('gems'), and adds a concrete use-case example ('sapphire or diamond for an everyday ring'). This distinguishes it from sibling tools like gem_properties (likely single-gem lookup) and search_gem_inventory (inventory search).

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 use-case example indicating when to use this tool (choosing between two gems for durability). It does not explicitly mention when not to use it or name alternatives, but the example and focus on hardness/toughness imply it is for comparing two specific gem species, not for general property lookups. This is adequate context without explicit exclusions.

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