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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is given; the description adds genuinely new context an agent could not infer: $0.001 USDC per successful call via x402 on Solana, plus the equivalent HTTPS endpoint. It does not say what happens on failure or whether failed calls are billed.

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 core definition and examples, with billing and endpoint details trailing where a non-interested agent can skip them; the example sentence is dense but every example earns its place by disambiguating semantics.

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-integer pure function with no output schema, the description covers domain, edge case, sample mappings, cost model and transport, which is essentially everything needed to invoke it correctly; only error/failure and payment-failure behavior are unaddressed.

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 load — and it does: it restates the valid domain (1 to 1e12) and, more usefully, supplies input→output examples that pin down the exact semantics of n, including the edge case n=1 returning 1.

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 the exact computed resource ('the largest prime factor of n') and anchors it with four worked examples (1→1, 12→3, 30→5, 35→7), so an agent can distinguish it from factoring siblings like smallest_prime_factor or prime_check without opening the schema.

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 worked examples plus the stated domain imply when the tool applies, and the pricing line implies pay-per-call usage, but there is no explicit guidance on when to prefer this over smallest_prime_factor, prime_check, or a full factorization path.

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