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

No annotations are present, so the description carries the full burden — and it largely succeeds: it discloses the operative behavior (deterministic constant retrieval), the returned value, and the lack of input requirements. The only omissions are minor for such a trivial tool: the exact return format/precision and an explicit read-only/idempotent statement, both easily inferred.

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?

Ten words across two sentences, with every element earning its place: purpose, the concrete value, and the input requirement. The core fact is front-loaded and there is zero filler or repetition of schema 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 zero-parameter, no-output-schema constant getter, this is nearly complete: purpose, value, and input requirements are all covered. The real gap is the unresolved relationship to sibling x402-golden-ratio, plus a slightly unspecified return format — both minor for a tool this simple.

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?

With zero parameters and 100% schema coverage, the baseline is 4. The description adds explicit confirmation with 'No input needed', which reassures the agent that the empty schema is intentional rather than incomplete. This is a slight value-add over the schema alone.

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 names a specific verb and resource: 'Return the golden ratio (1.61803...)' — unambiguous and self-contained. However, the sibling list includes x402-golden-ratio, which plausibly does the same thing, and the description does not differentiate x402-golden from it. Clear purpose, but no sibling distinction.

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' implies this tool is appropriate when the agent simply needs the golden-ratio constant, but there is no explicit when-to-use guidance. The near-duplicate sibling x402-golden-ratio is never addressed, so an agent must guess which to choose. Usage context is implied, not stated.

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