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

With no annotations present, the description carries the full burden, and it does add one genuinely useful operational detail beyond the schema: '5 free trial calls per signed wallet', i.e. a payment/auth prerequisite. Beyond that it says nothing about determinism, units conventions, or error behavior, so it is only partially compensating for the missing annotations.

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?

The result is stated in the first clause and the pricing caveat is appended compactly; nothing is repeated or padded. It is a single efficient sentence, though the trailing marketing fragment slightly dilutes the core purpose.

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 single-value math tool with no output schema, the description does state what is returned (exterior angle in degrees), which is the essential return information. However, it leaves the two-parameter ambiguity unresolved and gives no domain constraints, so an agent could still call it incorrectly.

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% and the two parameters ('n' and 'sides') are both undescribed strings, so it is unclear whether they are aliases for the same value, which one is authoritative, or what input format is accepted. The description's phrase 'number of sides' loosely maps to 'sides' but leaves 'n' completely unexplained and never states the valid domain (n >= 3, integer).

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 gives a specific verb and resource ('Returns the exterior angle in degrees of a regular polygon') plus the key input ('given number of sides'), which lets an agent distinguish it from x402-regular-polygon-interior and x402-interior-angle-sum. It stops short of naming those siblings explicitly, so it isn't a top-tier differentiator.

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 guidance and no routing to alternatives such as regular-polygon-interior or interior-angle-sum, which are the obvious near-neighbors in the catalogue. The phrase 'with the given number of sides' only implies what input is expected, not when this tool should be chosen over a sibling.

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