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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds genuinely non-structured context: the per-call price in USDC/Solana, the x402 payment requirement, and an equivalent HTTPS endpoint. It does not say what happens on out-of-range n, but the schema bounds cover that.

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?

Three compact sentences that lead with the definition, then examples, then constraints and access details. Pricing and endpoint information is a little tangential to the computation but is legitimately useful for an agent that has to pay for the call.

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, read-only sequence tool with no output schema, the description supplies the definition, a concrete output format via examples, the valid domain, the cost, and an alternate transport. Nothing further is needed to call it correctly.

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%, so the description must define n. It does: n is the number of leading bits, valid from 1 to 4096, and the n=8 / n=16 examples make the indexing convention unambiguous. The range restates the schema bounds rather than adding to them, keeping it short of a 5.

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 precisely what is returned: the first n bits of the Fibonacci word, with sample outputs for n=8 and n=16. The 'prefix' framing distinguishes it from the sibling 'fibword', but the sibling is never named or contrasted, so an agent must infer the boundary.

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 statement of when to use this versus fibword, thue_prefix, kolakoski_prefix, ruler_prefix, or hof_q_prefix. The description is a fact sheet, not usage guidance; the only implicit cue is that n is a bit count rather than an index.

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