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

With no annotations, the description carries the full behavioral burden. It usefully discloses the x402 payment requirement ($0.01/call, USDC, eip155:8453), which is real context an agent needs, but says nothing about rounding/precision, invalid-unit handling, or error behavior.

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 sentences, front-loaded with the capability and unit list, then the usage cue. No padding, though the trailing payment clause is boilerplate rather than substantive.

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?

No output schema and no annotations, so the description should say more about the result (unit of returned value, precision). For a simple stateless conversion it is adequate, but return-format expectations are left to inference.

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% but the parameter descriptions are placeholders ('To', 'From', 'Value'), so the description's expansion of enum abbreviations into full unit names (km=kilometers, um=micrometers, nmi=nautical miles) is the main source of meaning. It adds modest value beyond the abbreviations.

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 and resource (convert length units) and enumerates the full unit set, which cleanly separates it from sibling converters (area, weight, temperature, speed). An agent can identify it immediately.

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?

It gives a when-to-use cue ('when an agent needs to metric and imperial distance units, instantly'), though the sentence is grammatically broken and vague. It never names alternatives or exclusions, so routing among the many sibling converters is only implied by the unit list.

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