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

Annotations already declare a safe, idempotent read, and the description adds genuinely new operational context: a per-call cost of $0.001 USDC via x402 on Solana and an equivalent HTTPS endpoint. That payment/auth requirement is exactly the kind of information annotations cannot convey. It stops short of describing pagination or performance characteristics, which are less relevant for a bounded 1-5000 range.

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 core definition, then examples, then bounds, then pricing/endpoint — a sensible order. Every sentence carries information, though the four example points are slightly more than strictly necessary for a one-parameter tool.

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-parameter, no-output-schema tool, the description covers semantics, bounds, example outputs (implicitly revealing the integer return), and the billing model. It is nearly self-sufficient; only the exact return type is left implicit through examples.

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 description coverage is 0%, so the description must carry the load, and it does: the single parameter n is defined semantically ('how many ... at most n') and given a valid range plus four concrete value-to-result mappings. Only the type (integer) 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 operation (count of Duffinian numbers) and a precise scope ('at most n'), with worked examples that disambiguate the counting convention. It does not explicitly distinguish itself from siblings like duffinian, duffinian_sum or duffinian_next, though the 'count' prefix convention makes it inferable.

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 domain constraint ('n runs from 1 to 5000') and concrete sample inputs implicitly tell the agent when the tool applies, but there is no explicit when-to-use vs. the sibling duffinian/duffinian_sum/duffinian_next tools. Usage is implied rather than stated.

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