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

Goes well beyond the annotations by disclosing cost ($0.02/call via x402, USDC on Base), that errors are not charged, that data refreshes hourly and repeated calls return identical values, and the built-in TVL/outlier filters. These are exactly the operational facts an agent needs and none are in the structured fields.

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 purpose then usage, return shape, filters, and pricing in order. It is dense and long for a single paragraph, but each sentence (cost, freshness, filters, return fields) carries distinct, useful information rather than padding.

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 enumerates the returned fields (project, chain, symbol, tvlUsd, apy, apyBase, apyReward, apyMean30d, stablecoin, exposure, ilRisk, poolId) plus ordering and caps, and covers cost and freshness. Nothing needed to invoke it correctly is 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 the baseline is 4; the description confirms 'Call GET with no parameters,' removing any ambiguity about whether arguments are expected.

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 resource ('DeFi yields and APY') and scope ('stablecoin and DeFi pools'), and names the distinguishing use case, letting an agent separate it from siblings like money_market_rates or funding.

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?

Gives clear when-to-use guidance ('Use when you need to compare current DeFi pool yields, especially stablecoin or single-asset pools') but never names an alternative sibling tool or states when NOT to use it, so the routing is implied rather than explicit.

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