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

Annotations already cover read-only, idempotent, non-destructive behavior, but the description adds genuinely new operational context: a $0.001 USDC x402/Solana charge per successful call and an equivalent HTTPS endpoint. It doesn't explicitly state that the return is a boolean, though the 'Whether...' phrasing strongly implies it.

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-loaded with the definition, then supporting examples, then range, then cost and transport — every sentence earns its place and no wording is redundant with the title.

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 one-parameter predicate with no output schema and full annotation coverage, the description supplies the mathematical definition, examples, input domain, and payment/transport details. The only omission is an explicit statement of the boolean return, which would fully close the loop.

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?

There is one parameter with 0% schema description coverage, so the description must compensate — and it does, defining n as the number whose quotient by its digit sum is tested and bounding it to 1..5000. The only gap is that the 1..5000 range duplicates the schema's min/max rather than adding new constraints.

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 n divided by its digit sum is prime — with worked positive (18, 21, 27) and negative (1, 10, 12, 24) examples, which is far more concrete than typical in this family. It doesn't explicitly distinguish itself from close siblings like moran_count, moran_next, or moran_ratio, though the family naming and the example-driven formulation make the single-value test implied.

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: 'n runs from 1 to 5000' gives the valid input domain, and the examples show what a true/false answer looks like, but there is no explicit when-to-use-this vs moran_count/moran_next guidance or statement of what to do for out-of-range n. An agent can infer the use case from the naming, but nothing is spelled out.

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