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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the description adds value beyond that by listing the complete set of supported units and the exactness conditional. No contradictions with annotations; this is a pure, side-effect-free conversion operation.

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 a single purposeful sentence with a necessary unit list. It is front-loaded with the action and categories, and the trailing usage hint is concise. The long unit list is justified by the need to enumerate accepted values, so it earns a high but not perfect score.

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 3 required parameters and an output schema, the description covers the unit inventory and use case, making it functionally complete. It does not explain error behavior for incompatible units, but the schema's 'from'/'to' descriptions already convey the constraint. Overall, the agent has enough context to use 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?

Although the schema describes all parameters, it lacks enums for 'from' and 'to'. The description compensates by providing an exhaustive list of valid units, which is essential for correct invocation. This goes beyond the minimal schema descriptions and adds significant meaning.

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?

Description states a specific action ('Convert a value between units') and enumerates the categories (length, mass, data size, time, speed, temperature), distinguishing it from sibling conversion tools like base_convert or color. The title 'Convert between units' is reinforced by the detailed scope.

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 instruction 'Use for exact conversions instead of approximating' provides clear usage context, implying this tool should be chosen when precise conversion is needed. It does not explicitly name alternatives or exclusions, but the context is sufficient for an agent to decide when to invoke it.

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