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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=false, so the safety profile is covered. The description adds genuine behavioral value rare for converters: it pins the exact convention (thermochemical calorie = 4.184 J, IT BTU as opposed to thermochemical BTU), which prevents silent off-by-factor errors.

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 dense sentence: action verb, unit list, and conversion constants, front-loaded with zero filler. Nothing is redundant with the name or annotations.

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?

An output schema exists, so return values need no explanation, and the annotations cover the safety profile — the description supplies the remaining piece, the unit set and one conversion constant. The residual gap is that accepted unit strings are never spelled out in a way that matches the schema examples, which matters for a tool with no enums.

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%, setting a baseline of 3, but the schema has no enums, so the description is the only place the accepted unit vocabulary is stated. It adds meaning beyond the schema, though the exact token spelling (e.g. 'cal' vs 'thermochemical cal', 'BTU' vs 'IT BTU') remains ambiguous relative to the schema's 'J'/'kWh' examples.

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 (energy) and enumerates the supported units, which distinguishes it from the broad calculator_convert sibling. It does not explicitly contrast itself with calculator_power_convert or calculator_unit_constants, so sibling differentiation is only implicit.

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?

Listing J, thermochemical cal, kWh and IT BTU implies the usable scope (only these energy units), but there is no explicit when-to-use guidance, no statement about unsupported units or errors, and no pointer to the generic calculator_convert alternative.

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