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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds the supported units and a source URL but does not disclose rounding, precision, or edge-case behavior; it does not contradict the 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?

Two short sentences: the first is front-loaded with the operation and unit list, the second adds a source. There is no filler or redundant repetition of schema information.

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 conversion tool with 100% schema parameter coverage, an output schema, and safety annotations, the description is sufficient. The unit list plus parameter schema gives the agent everything needed to invoke 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 coverage is 100%, so the description does not need to explain the parameters exhaustively. It adds value by expanding the abbreviation meanings 'in (inches), ft (feet), yd (yards), mi (miles)', which helps agents map user requests to the enum values correctly.

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 states the specific verb 'Convert' and the resource 'a length from one unit to another', then enumerates the exact supported units. This clearly differentiates it from area, weight, volume, and speed converters in the sibling list.

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 supported-unit list gives the agent a clear sense of when the tool applies, but the description does not explicitly state when not to use it or contrast it with specialized siblings like hopi_cm_to_feet or hopi_miles_to_km. The usage context is implied rather than explicit.

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