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

No annotations are supplied, so the description carries the full disclosure burden. It is a stateless pure calculation with no side effects, and its brevity implicitly conveys that, but it says nothing about rounding/precision, output formatting, or behavior for the optional target unit being omitted.

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?

A single front-loaded sentence with zero wasted words; the verb, the value being acted on, and the unit scope all land immediately.

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?

With a full output schema and 100% parameter coverage, the description does not need to explain return values. It is adequate for this simple tool, though it could note the all-units fallback and any precision behavior to be fully self-contained.

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 100%, so the enum values and the 'optional target unit; all units returned when omitted' semantics are already documented in the schema. The description merely repeats the unit list and adds no syntax or format detail beyond it, matching the baseline 3.

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 ('Convert') and resource ('a distance value') plus the exact unit set, which unambiguously separates it from siblings like convert_power, convert_speed, or convert_torque. An agent can select it without opening the schema.

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 purpose itself — you call it when a distance needs converting — but there is no explicit when/when-not guidance and no mention of the notable 'omit `to` to receive all units' mode, which is the one routing decision this tool actually has.

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