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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower, and the description still adds non-schema facts: a per-call price of $0.001 USDC via x402 on Solana and an equivalent HTTPS endpoint. That commercial and transport context is exactly what annotations cannot convey.

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 answer predicate is front-loaded in the first clause, followed by examples, bounds, and then the pricing/endpoint note. Every sentence carries information, though the example list is slightly longer than needed.

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 covers input domain, member/non-member examples, and access mechanics. The one gap is that it never says the return is a boolean verdict rather than, say, the step sequence, though 'Whether' strongly implies it.

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% and the only parameter has an obvious name, but the description does add meaning: the range of n and concrete examples of members versus non-members. It does not explain why 10 and 11 fail or how the digit-based construction works, so the semantic lift is only moderate.

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 predicate: "Whether n is a Keith number," with a verb-and-resource pairing an agent can act on immediately. It does not name its close siblings (keith_count, keith_next, keith_row, keith_steps), so the boundary with those is left implicit.

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 description supplies worked examples of true and false cases and the valid input range, which helps an agent build calls, but it never says when to choose this check over keith_steps, keith_row, or keith_count. No exclusions or alternative routing are given.

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