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

With zero annotations the description carries the full burden, and it discloses the most consequential behavioral fact: the tool is paid (0.01 USDC on Base via x402, or 12 sats Cashu NUT-24, or 12 sats Lightning L402). That payment gating and protocol detail is real value an agent cannot get elsewhere. It stops short of describing failure behavior or output shape.

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 domains, then the cost clause. Every element is relevant. The payment enumeration is dense but earns its place given it is a hard gate on invocation.

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 3-param converter with no output schema and no annotations, the description covers purpose, domains, an example call, and payment — enough to attempt a call. It is missing the enumerations an agent needs to avoid an invalid unit code, which is the main remaining gap.

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%, so the description must compensate for three undocumented required params. It partially does: the example shows value as a numeric string and from/to as short unit codes (mi, km), and the domain list hints at valid unit families. However, it never enumerates acceptable unit symbols or case sensitivity, leaving real ambiguity for temperature and data-size units.

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 (unit conversion) plus the full set of supported domains (length, mass, volume, speed, area, data size, time, temperature), which tells an agent exactly what is and isn't convertible. None of the ~40 siblings perform unit conversion, so no sibling ambiguity exists.

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?

The inline example (value=10&from=mi&to=km) implies how to invoke it, and the payment sentence implies a prerequisite for use, but there is no explicit when-to-use guidance, no statement of when another tool applies instead, and no note on unsupported conversions or error conditions.

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