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

Annotations already declare readOnly, idempotent, non-destructive and openWorld, so the safety profile is covered; the description goes beyond by disclosing the paid x402/Solana cost ($0.001 USDC per successful call) and an equivalent HTTPS endpoint, which materially affects whether an agent should invoke it. It does not state the return form explicitly, leaving 'whether' to imply a boolean.

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?

Front-loads the definition and example before commercial details, and each sentence adds something (definition, example, domain, price, alternate transport). Slightly dense with the endpoint URL appended, but no filler.

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 single-integer predicate with no output schema, the description supplies the definition, domain, example, cost and transport. Adequate to call correctly; the only gap is not stating outright that the result is a boolean.

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 carry the burden, and it does define what n means (a number whose decimal digit sum must divide it) and gives the exact domain 1 to 999999999999999, matching the schema bounds. Only the integer type itself is left to the schema.

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 (test whether) and a precisely defined resource (base-10 Harshad number), with the defining formula and a worked positive/negative example (18 yes, 11 no). The explicit 'base-10' qualifier separates it from the sibling harshad_base, so an agent can pick between them without opening schemas.

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: an agent can infer this is the tool for a plain Harshad test in base 10, but the description never says when to prefer harshad_base, nor states any exclusions or prerequisites beyond the numeric domain.

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