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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive. The description adds important behavioral context beyond those: the call costs $0.001 USDC via x402 on Solana, and there is a parallel HTTPS endpoint. It still does not explicitly state the return type or failure behavior, but the payment and endpoint details are substantial additions.

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 description is short and front-loaded with the predicate and examples, then moves to range and payment details. Every sentence adds some value, though the range repeats the schema and the payment/endpoint lines could be slightly more clearly separated.

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 predicate tool with rich read-only annotations and no output schema, the description is nearly complete: it defines the condition, gives qualifying and non-qualifying examples, states the valid input range, and discloses the payment model and alternate endpoint. The main omission is an explicit statement that the tool returns 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 description coverage is 0%, so the description must carry the meaning of n. It does so by explaining the mathematical property being tested ('every base-4 digit of n is 0 or 1') and by giving examples (0, 1, 4, 5, 20 qualify; 2, 6 do not). The stated range (0 to 1e12) duplicates the schema minimum and maximum, but the property definition compensates substantially for the missing schema descriptions.

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 defines the predicate precisely: 'Whether every base-4 digit of n is 0 or 1,' and gives examples that qualify or not. It does not explicitly say 'check if n is a Moser number' or distinguish the operation from siblings such as moser, moser_count, moser_index, and moser_sum, but the condition itself makes the purpose clear.

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?

No when-to-use or when-not-to-use guidance is given. The description never mentions alternatives like moser_sum or moser_index, so an agent must infer that this tool is only for membership testing and not for generating terms, counts, or sums.

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