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

No annotations are provided, so the description carries the full behavioral burden, yet it discloses nothing: not what an 'efficiency' result means, in what units, whether inputs are numeric or strings despite being typed as strings in the schema, 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?

Brevity here reflects under-specification rather than conciseness; the single fragment 'Efficiency: Efficiency calculation.' repeats itself and earns no place.

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 no annotations, no output schema, and two undocumented string parameters, the description is wholly inadequate for an agent to invoke this tool correctly.

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 schema descriptions are themselves circular ('InputWork to process', 'OutputWork to process') and the parameter types are string, which for an efficiency calculation is surprising. The description adds no meaning beyond the field names, so it fails to compensate for the effectively non-existent schema documentation.

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 'Efficiency: Efficiency calculation.' is a tautology that merely restates the tool name x402-efficiency. It names no verb, no resource, no input/output relationship, and gives the agent no way to distinguish it from any other math utility among the hundreds of x402-* siblings.

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 when-to-use guidance, no prerequisites, and no mention of any alternative tool. An agent has no basis to decide whether this is the right tool versus e.g. x402-throughput-humanize or x402-power.

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