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

Goes well beyond the readOnly/idempotent/non-destructive annotations by disclosing the return format (comma-separated list through n), failure behavior for non-Keith inputs, the valid input range, and unusually valuable operational facts: a $0.001 USDC charge per successful call via x402/Solana plus an alternate HTTPS endpoint. Cost and payment requirements are exactly the kind of context 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?

Front-loads the operation and the example, then error behavior, constraints, and finally price/endpoint. Dense but every sentence carries information; the HTTPS line is scaffolding rather than tool semantics but is short.

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?

A one-parameter tool with no output schema, and the description covers return format, error behavior, input range, and payment model. Nothing an agent needs before calling is missing.

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 burden. It clarifies that n is the Keith number whose digit recurrence is emitted (via the 14 example) and states the range 1–1000000, which duplicates the schema's min/max but the worked example genuinely adds semantic meaning the schema lacks.

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+resource: it returns the digit recurrence (the 'row') of a Keith number through n, illustrated with "14 gives 1,4,5,9,14". That is distinguishable from siblings keith (probably a check), keith_count, keith_next, and keith_steps, though none of those siblings are named explicitly.

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 ('a number that is not Keith is rejected') implicitly tells the agent this is only for Keith inputs, and the n range bounds usable inputs. But there is no explicit guidance on when to pick this over keith_steps or keith_next, and no statement of alternatives.

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