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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered. The description then adds genuinely useful non-schema context: cost ($0.001 USDC per successful call, x402 on Solana) and a same-function HTTPS fallback endpoint, both of which affect invocation strategy.

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?

Definition first, then examples, then domain, then cost/transport — correctly front-loaded with zero filler. Every sentence carries distinct information an agent needs.

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 no-output-schema, single-parameter pure function, the description supplies definition, examples, valid range, pricing, and a transport alternative — enough to call it correctly and know the return semantics from the examples. Only the explicit output type/format is left implicit.

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% for the single parameter, but the description compensates by restating the valid domain and, more importantly, giving the edge-case behavior at n=1 (returns 0) plus two concrete input/output examples. A small gap remains: nothing states the return type or performance expectations for very large n.

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 a precise mathematical definition (sum of prime factors with multiplicity), which inherently distinguishes it from the sibling sopf (distinct prime factors). Worked examples (sopfr(1)=0, sopfr(12)=7, sopfr(36)=10) pin down the semantics unambiguously.

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 'with multiplicity' qualifier plus the domain constraint ('n runs from 1 to 1000000000000') tell an agent exactly what scope is valid and implicitly which sibling to prefer for the distinct-factor variant. There is no explicit when-not-to-use or a named alternative, so it falls short of a 5.

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