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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description goes well beyond them by disclosing the exact cost ($0.002 USDC), the in-call payment mechanism (x402 on Base/Solana/Polygon/Arbitrum), and that compatible clients like @x402/mcp auto-pay — critical behavior an agent must know before invoking.

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-loads the value proposition (what data comes back), then cost/payment, then the free-sample escape hatch. Dense but organized; the payment detail is long yet necessary, so only a minor deduction for density.

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 must carry the return contract, and it explicitly lists every returned field including per-validator APY/commission/stake and sort order. Cost, payment chains, and the free trial are all stated, leaving nothing an agent needs missing.

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?

Zero parameters, so per the rubric the baseline is 4. The schema confirms an empty object and the description reinforces it with 'call with the example input {}', adding as much param context as a no-arg tool allows.

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 a specific verb+resource ('Sui mainnet in one call') and enumerates the exact payload: epoch, latest checkpoint, reference gas price, SUI price, total stake, and per-validator staking APY/commission/stake. This clearly separates it from siblings like sui_tx, sui_watch, sui_address, and iota_network without opening any 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?

Provides the free-sample path ('call with the example input {}') and implies it is a paid aggregator, but never says when to prefer this over sui_tx or sui_watch or what conditions make it the right pick. Usage is implied rather than stated, so it lands at the minimum-viable tier.

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