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

With no annotations, the description carries the full behavioral burden. It does disclose the output direction and the exact conversion rate (0.00134102 hp per watt), which is useful. But it says nothing about units accepted, rounding, error behavior, or how the two schema inputs relate, leaving the core behavior only partially described.

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 front-loaded sentence with no filler; the parenthetical conversion factor earns its place by pinning down the exact rate. It stops just short of ideal because it omits any direction/unit qualifier that would prevent misreading.

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 unit converter with no output schema and no annotations, a short description is largely sufficient, and the conversion factor is a helpful addition. However, the mismatch between the described input and the actual time/work parameters, plus the lack of any sibling disambiguation, leaves the definition incomplete for correct invocation.

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 two documented parameters ('time', 'work') do not match the description's stated input ('value in watts'), so the description and schema actively conflict rather than reinforce each other. A caller following the description would look for a watts parameter that does not exist, and the schema's own descriptions ('Time to process') are too generic to resolve the 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?

The description states a specific verb and resource (convert power between watts and horsepower) and even gives the exact conversion factor, so the operation is clear. It does not, however, distinguish itself from the near-identical siblings x402-watts-to-horsepower and x402-horsepower-to-watts, leaving the agent unsure which to pick.

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 explicit guidance on when to use this tool versus alternatives, despite the sibling list containing direct competitors (x402-watts-to-horsepower, x402-horsepower-to-watts, x402-power-unit, x402-electric-power). The only hint is the implied input direction ('provide value in watts'), which is not framed as a selection rule.

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