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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds real capability context beyond that: the breadth of unit categories supported and the fact that arbitrary math expressions, constants, and matrices can be evaluated safely rather than just scalar conversions.

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 opening 'Convert units of measure. Convert units.' repeats the title and name with zero added information, which is wasted space. The remaining sentence is dense and informative, but the duplication weakens the front-loading.

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?

There is no output schema, so the description should ideally indicate the return shape (e.g., converted value with unit) and behavior on invalid or mismatched units. It covers input scope well but leaves the return value and failure behavior unstated for a tool whose whole job is producing a converted result.

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 coverage is 100%, so each parameter is already documented in the schema, and the baseline is 3. The description hints that the 'value' parameter accepts expressions, but never states this mapping explicitly, so it adds little semantic value beyond the schema.

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?

States a specific verb+resource (converting units of measure) and enumerates categories and capabilities (300+ units, expression evaluation with functions/constants/matrices). However it does not distinguish itself from close siblings such as convert_currency, convert_calendar_date, or convert_time_zone, leaving ambiguity about scope boundaries.

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?

Usage is implied by the tool's nature, but there is no explicit when-to-use guidance and no named alternative. In particular, an agent cannot tell from the description whether currency conversion belongs here or in convert_currency, which is a meaningful routing gap given the sibling list.

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