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

With no annotations, the description carries the full burden; it does add the pricing/quota context ('5 free trial calls per signed wallet'), which is genuinely useful and not available elsewhere. However, it doesn't say what happens after the free trial (payment required, error, rate limits) or the return type/precision beyond an example value.

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 plus a quota note; the value and the no-input fact are front-loaded. The emoji is decorative noise but does not obscure meaning.

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 zero-arg constant with no output schema, the description covers input contract, expected value, and the cost model. Only the post-trial payment behavior and exact output format are unstated, which are minor for this complexity.

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?

Zero parameters, so baseline is 4; the description confirms the no-input contract explicitly rather than leaving it to the empty schema, which is a small but real addition.

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 and resource ('Return the square root of 3') and even pins the value (1.73205...), which immediately separates it from siblings like x402-sqrt2 or x402-pi.

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 input needed' tells the agent how to invoke it, but there is no explicit guidance on when to prefer this over x402-sqrt2 or x402-pi, nor any stated exclusion. Usage is implied by the constant nature rather than spelled out.

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