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

Beyond the annotations, the description discloses the data provenance (DefiLlama yields) and a full billing model: $0.002 in USDC per successful call via x402 on Base, Solana or Arc, with failed calls uncharged. That payment and cost detail is actionable context an agent cannot get from readOnlyHint/openWorldHint.

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?

Three compact sentences: what is reported, what is excluded, and what it costs. The coverage statement is front-loaded and the exclusion follows immediately, with no filler.

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 an output schema present, return values need not be described, and the description covers scope, exclusions, provenance and pricing. The one gap is freshness/update cadence for APY figures, which matters for a rates tool and is left unstated.

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?

The tool takes no parameters, so the baseline is 4; there is nothing for the description to disambiguate. It does not state whether optional filters exist because none do, which is appropriate.

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 names the exact resources (sUSDS/sDAI savings APY and TVL, DAI/USDS price, depeg %, circulating supply) and their sources (DefiLlama yields, Ethereum). It also pre-empts the mismatch created by the tool name by stating that vault collateralization is not reported, letting an agent separate it from siblings like crypto_lido_steth_peg or crypto_defillama_stablecoins.

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 an explicit negative scope: 'Vault collateralization is not in these sources and is not reported,' which tells the agent when not to call it despite the name. It does not, however, name a specific sibling to use instead for collateralization data, so the agent must still infer the alternative.

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