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 genuinely useful behavioral facts: it is a paid call ($0.001 USDC via x402 on Solana) with an equivalent HTTPS endpoint. What it omits is failure behavior — whether a failed call is charged, and any rate limits or authentication/payment handshake details.

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-loaded with the definition, then examples, then the input bound, then cost/transport. Four short sentences, each carrying distinct information; nothing is redundant.

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?

With no output schema, the description carries the return-value burden and mostly does so via the fraction examples, plus it discloses pricing and the alternate endpoint. The remaining gap is the wire format of the result (e.g., string "7/4" vs. a numerator/denominator object), which an agent would want before parsing.

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%, but the single parameter is fully compensated for in prose: the description states the domain (n from 1 to 1000000000000) and multiple concrete n → result mappings that make the semantics of n unmistakable. It does not restate that n must be an integer, but the examples make that evident.

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 states a precise computation (sigma(n)/n as a reduced fraction) and backs it with worked examples (1 → 1/1, 12 → 7/3), so an agent knows exactly what the tool returns. It falls short of 5 because it never distinguishes itself from the close sibling `abundance` (or `divisor_sum` / `sigma_k`), leaving ambiguity about which of these near-identical number-theory tools to call.

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?

Usage is only implied: give an integer n in [1, 10^12] and receive the abundancy fraction. There is no explicit when-to-use, no mention of when NOT to use it, and no routing to `abundance`, `aliquot`, or `sigma_k` despite a very dense sibling namespace.

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