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

No annotations are provided, so the description carries the full burden. It does disclose a real behavioral constraint — 5 free trial calls per signed wallet — which tells the agent there is a quota and a wallet requirement. But it says nothing about what happens after the trial, error behavior, or how the conversion result is shaped.

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 core action. The 'Distance:' prefix slightly duplicates the tool name, and the emoji pricing clause is a bit of a non-sequitur, but there is no filler.

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 three-parameter conversion tool with no annotations, no output schema, and 0% parameter documentation, the description leaves critical gaps: which units are valid, what the return value looks like, and how it differs from the many conversion siblings. The quota note is the only substantive addition.

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 0%: the three parameters (to, from, value) are bare names with no types beyond string and no descriptions. The description does not identify the supported unit vocabulary, whether 'value' accepts numeric strings only, or case/abbreviation conventions. With three undocumented params, the description should compensate and does not.

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 between distance units'. An agent can immediately tell this is a unit-conversion tool. However, it offers no differentiation from the many conversion siblings (x402-units-convert, x402-length, x402-km-to-miles, x402-meters-to-feet), so the boundary is unclear.

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 guidance on when to use this versus the numerous sibling conversion tools, nor any prerequisites or exclusions. The only extra sentence concerns free trial quota, which is pricing context rather than usage guidance.

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