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

With no annotations, the description carries the full behavioral burden, and 'Pure CPU, instant' does usefully disclose that this is a local, side-effect-free, low-latency computation. It stops short of confirming the operation is non-destructive, what happens on an unrecognized unit string, or what the response looks like.

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?

Two short sentences, front-loaded with the resource and the supported units, with no filler wording. Every phrase contributes 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 simple three-parameter calculator with no output schema and no annotations, the description covers purpose and unit vocabulary but not the calling contract: only 'value' is required, yet nothing says how 'from'/'to' behave when omitted, nor is the return value shape mentioned. Adequate but with clear gaps for a tool whose schema carries no enums or meaningful param docs.

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 nominally 100%, but the schema descriptions are near-empty placeholders ('Target unit', 'Source unit', 'Value'), and there are no enums. The description's unit list (km/h, mph, m/s, knots) is therefore the only real guidance on accepted values, which is genuine added meaning. It still omits whether 'from' and 'to' are optional and what defaults apply.

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 gives a specific verb plus resource (convert speed units) and enumerates the supported units (km/h, mph, m/s, knots), so the agent knows exactly what domain this covers. It does not distinguish itself from generic siblings like unit_convert or convert_units, leaving that routing decision to inference.

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 only implied by the unit domain; there is no explicit statement of when to use this versus the generic unit_convert/convert_units tools or the other per-dimension converters (distance, pressure_convert, energy_convert). 'Pure CPU, instant' hints that it is a local, no-IO calculation, but no exclusions or alternatives are named.

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