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

With no annotations, the description carries the full burden. It discloses the computation and the payment/trial constraint ('5 free trial calls per signed wallet'), which is genuine behavioral context. However, it says nothing about input handling (why parameters are strings), numeric edge cases, or error behavior, so the disclosure is partial.

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?

One front-loaded sentence delivers the computation and formula with no wasted words. The trailing trial/pricing tagline is x402 boilerplate rather than core function, but it is short and does not bury the essential content.

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 trivial two-parameter math tool with no output schema, the description supplies the operation, the formula, and the return value, which is nearly everything an agent needs. Only input typing/edge-case behavior is left unspecified.

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% and the properties are opaque single letters 'a' and 'b', but the description compensates by identifying them as 'two legs' and tying them to the a² + b² formula. It does not explain the string typing or expected formats, so coverage remains partial.

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+resource ('Returns the hypotenuse') and even gives the exact formula (sqrt of a² + b²), so an agent immediately knows this computes a hypotenuse from two legs. It doesn't explicitly name the sibling x402-pythagorean-leg, but the direction of computation (hypotenuse, not leg) is unambiguous.

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?

No when-to-use or when-not-to-use guidance is given, and no alternative is named despite a sibling x402-pythagorean-leg existing. The '5 free trial calls' note is pricing, not usage routing, so the agent must infer applicability from the function alone.

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