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

Annotations already declare readOnly, idempotent, non-destructive, and openWorld, so the safety profile is covered. The description adds genuinely useful context beyond that: a per-call price of $0.001 USDC via x402 on Solana (an auth/payment requirement) and the fact that terms past 15 digits return as decimal strings. It does not describe the return shape for smaller terms beyond that hint.

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 formula leads, which is good, but the 'a through f' sentence is confusing noise given those are not inputs, and the pricing/URL add bulk. It is reasonably compact but not every sentence earns its place.

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 read-only compute tool with no output schema, the description covers the recurrence, range, large-number output format, and payment model. It leaves two real gaps: the seed values behind a-f are never explained (so the agent cannot tell if defaults are used), and it never states the return value explicitly.

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 there is one parameter, so the description should carry the burden. It does explain n's role (index 6-512) but only repeats the schema's min/max bounds, and the sentence about 'a through f' as the six earlier terms introduces names that do not exist in the schema, muddling rather than clarifying the single input.

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 gives the exact recurrence H(n)=sum of previous six and names the tool's role in a hexanacci sequence. However, it never states plainly what the call returns (presumably H(n)) nor how it differs from sibling hexanacci, hexanacci_index, or hexanacci_sum. The central purpose is inferable from the formula but not spelled out.

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?

There is no guidance on when to use this step tool versus the sibling hexanacci/hexanacci_sum/hexanacci_index tools. The only routing information provided is a pricing note and an HTTPS alternative endpoint, which addresses transport, not tool selection.

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