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

The description directly resolves the counterintuitive readOnlyHint=false annotation by explaining that reads/computes are not marked read-only because each call is charged. It further discloses pricing, a free tier, and that failed calls are free — genuinely useful behavioral context beyond the structured fields.

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?

Front-loaded with the conversion domain and example units, followed by usage, an example, and pricing. Dense but every sentence is relevant; the pricing sentence is the longest but conveys actionable cost/free-tier 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 low-complexity 3-param conversion tool with no output schema, the description covers domain, usage, example, and cost behavior adequately. It does not describe the return format, but the operation's single-value result is broadly implied.

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 baseline is 3, but the description adds value by listing concrete unit tokens (km, mi, lb, kg, gib, kwh) for params that have no enums, plus a filled-in example. This meaningfully supplements the terse schema descriptions like "Unit to convert to".

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 and resource (convert between units) and enumerates the supported categories and example units (km, mi, lb, ml, mph, gib, psi). No sibling tool performs unit conversion, so there is no risk of confusion with the rest of the toolkit.

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?

"Use when exact conversions matter" gives a clear context for reaching for this tool, and the worked example (value=10, from=km, to=mi) shows the intended call shape. There are no alternative conversion siblings, so the absence of explicit exclusions is not a real gap.

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