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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=true), so the bar is lower. The description adds genuinely useful context beyond them: the payload is 'pre-sanitized for AI execution' (relevant given the security_* siblings) and each call costs $0.002 USDC on Base, which is material cost behavior an agent must know before invoking. It does not state refresh cadence or rate limits.

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?

Two packed sentences with zero filler. The data scope is front-loaded, and cost/payment information is appended where it belongs.

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 no explanation, and annotations cover safety. The definition supplies source, asset scope, chains, sanitation status, and price — sufficient to invoke correctly. Missing only refresh cadence/latency for a 'Live' feed, which is a minor gap.

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 input parameters, so there is nothing for the description to disambiguate — baseline applies. The chain scope is stated in prose rather than exposed as a parameter, which is a minor opportunity missed but not a defect.

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?

Names a specific resource (top stablecoin & ETH APY yields), the data source (DeFiLlama), and the two chains (Base, Arbitrum) — an agent knows exactly what data comes back. It stops short of an explicit verb and does not distinguish itself from siblings, though none of the listed siblings overlap in domain, so routing is easy anyway.

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 by the resource type: an agent can infer it should call this when it needs live DeFi yield data. There is no explicit when-to-use, when-not-to-use, or named alternative among the many data-fetch siblings, so the agent must infer the context itself.

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