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

With no annotations, the description must carry the behavioral load. It usefully pins the output unit (degrees) and discloses a payment/rate trait ('5 free trial calls per signed wallet'), which are genuine beyond-schema facts. However it says nothing about determinism, invalid-input behavior (e.g. n < 3), or whether the call is free versus paid beyond the trial.

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 compact sentence front-loads the purpose, with the pricing tag appended after. No filler or repetition, though the emoji/trial-call banner is arguably marketing noise rather than definition 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 tool with two undocumented string parameters, no annotations, and no output schema, an agent needs at least the valid input range and which parameter to populate. Neither is provided, and the duplicate n/sides fields compound the ambiguity, leaving the definition under-specified for correct invocation.

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 description coverage is 0%, so the description must compensate and largely fails to. It refers to 'the given number of sides' but the schema exposes two ambiguous string parameters (n and sides) with no indication of which to use, their type/format, or valid range (integer >= 3).

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 ('Returns the interior angle in degrees of a regular polygon with the given number of sides'), which cleanly separates it from siblings such as x402-regular-polygon-exterior or x402-regular-polygon-area. The only gap is that it never names those siblings explicitly, but the unique noun 'interior angle' makes the distinction inferable.

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 or when-not-to-use guidance, and no alternatives are named despite nearby siblings (area, exterior, perimeter) that an agent could easily confuse. The description only tells the agent what the tool computes, not when to reach for it over those neighbors.

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