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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered by structured fields. The description adds nothing behavioral beyond that — no statement of rounding/precision, output formatting, or how ambiguous terms like 'ton (metric)' map to input strings — despite being the only prose source for such details.

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 short sentence with the resource and the unit vocabulary front-loaded, no filler. It is arguably over-terse rather than padded, so the only cost is missing detail, not wasted words.

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 an output schema present, return values need not be described, and all three parameters are documented in-schema, so the core is covered. For a units converter, however, accepted input spellings and rounding behavior are exactly the details that cause failed calls, and the description is silent on both.

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 genuinely adds meaning the schema lacks: the schema declares from_unit/to_unit as free strings with zero enums, and the description supplies the accepted unit vocabulary (mg, g, kg, ounce, pound, ton metric). It does not clarify whether abbreviations like 'oz' or 'lbs' are accepted, which is the remaining ambiguity.

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 (mass) and enumerates the supported units, so an agent can immediately tell this is not the length, volume, or generic unit converter. It never explicitly names the near-siblings calculator_convert or calculator_volume_convert, so differentiation is achieved by unit list rather than by direct statement.

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 description gives no when-to-use or when-not-to-use framing, and in a sibling set this large that matters: an agent deciding between calculator_weight, calculator_convert, calculator_mass-adjacent tools like calculator_molar_mass, or calculator_length gets no routing rule. Usage is only inferable from the unit list.

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