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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds genuinely new operational context: a per-call price of $0.001 USDC via x402 on Solana and an equivalent HTTPS endpoint, which explains the openWorldHint. What remains unstated is the return shape beyond the implied boolean and whether failures are charged.

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 predicate is front-loaded, followed by compact illustrative examples, then the range and payment/logistics line. Every sentence serves a purpose, though mixing mathematical definition with pricing and endpoint details in one paragraph is slightly jarring.

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 no output schema, the description does the necessary work by framing the result as a yes/no property and confirming it with example numbers, plus giving the domain, cost, and alternate endpoint. Only the exact return payload (boolean vs. object with the sum) is left implicit.

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 carries the burden, and it does identify n as the input and its valid range 1 to 1000000 — though that range merely restates the schema's minimum/maximum rather than adding meaning beyond it. No detail on type expectations or behavior at boundary values is added.

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 precise predicate: whether the bi-unitary divisors of n sum to more than 2n, and anchors it with worked true/false examples (24, 48 vs 6, 16, 36). That is enough to separate it from the biunitary_deficient/biunitary_perfect/biunitary_sigma siblings, although none of them is named explicitly.

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?

The input domain ('n runs from 1 to 1000000') and the example classifications imply when the tool is applicable, but nothing tells the agent when to prefer it over a sibling such as biunitary_sigma (the sum itself) or biunitary_count. Usage must be inferred from the name and predicate rather than stated.

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