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

Annotations already cover read-only, idempotent, open-world, non-destructive behavior, so the bar is lower. The description still adds material beyond them: a per-call price of $0.001 USDC via x402 on Solana and an equivalent HTTPS POST endpoint, which an agent needs to know before invoking a paid tool. It omits what the response payload looks like, but cost and channel disclosure is the important extra here.

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 core definition is front-loaded in the first sentence, followed by compact worked examples, then bounds, pricing, and endpoint. The four-example chain is slightly long but each illustrates a distinct transition (7→7, 16→14, 24→21). The range restatement is mild redundancy with the schema.

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?

With one parameter, no output schema, and annotations carrying the safety profile, the description covers what an agent needs: what is counted, the input domain, cost, and transport. The one gap is that it never states the return value is a single integer count, which an agent can infer but would prefer confirmed.

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%, so the description must compensate, and it largely does: 'at most n' defines n as the inclusive upper bound of the counted range, and range limits are restated. The 1-to-20000 bound duplicates the schema's min/max rather than adding to it, but the semantic definition of n is a real contribution.

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 first sentence states a specific verb and resource: it counts cubefree positive integers up to a bound n, which distinguishes it in practice from the membership-style `cubefree` sibling. It does not explicitly name siblings like `cubefree` or `squarefree_count`, so an agent must infer the split, but the counting semantics themselves are 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?

Usage is only implied. The worked examples (through 8 still 7, through 16 is 14) clarify edge behavior such as non-cubefree numbers being excluded, which is genuinely useful for interpreting a call. However, there is no explicit statement of when to use this versus `cubefree` or other counting tools, and no exclusions or prerequisites.

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