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

Annotations already declare readOnlyHint=true, non-destructive, and closed-world, so the safety profile is covered elsewhere. The only added behavioral information is the word "exact", which usefully signals these are precise definitional factors rather than rounded values. No mention of lookup semantics, partial-match behavior, or fallback when a key is unknown.

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 parenthetical with concrete conversion examples – no filler and the illustrative pairs are front-loaded. It is efficient, though the terseness edges into under-specification rather than pure economy.

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 and full parameter coverage, the schema burden is light, but in a catalog of ~130 calculator siblings the description must resolve the overlap with calculator_convert, calculator_math_constants, and calculator_scientific_constants and does not. An agent cannot confidently choose this tool from the description alone.

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%, with both `list` and `query` documented in-schema, so baseline is 3. The description does not explain the modes (list-all vs. single-key lookup), the accepted key naming convention (e.g. inch_to_meter vs. inch), or how the two parameters interact when both are supplied.

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 names a resource type (exact/conversion factors) with illustrative examples (inch→m, atm→Pa, kWh→J), so the domain is inferable, but it is a noun-phrase fragment with no verb telling the agent what the tool actually does (look up? return? compute?). It also never distinguishes itself from close siblings like calculator_convert, calculator_math_constants, or calculator_scientific_constants.

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?

There is no statement of when to use this tool versus calculator_convert (general conversion) or calculator_math_constants / calculator_scientific_constants (other constant catalogs). No precondition, no exclusion, and no mention that query can take a partial name like "inch" as shown in the schema examples.

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