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

Goes well past the annotations: discloses pricing ($0.02/call via x402, USDC on Base, MCP payments Base-only), that errors are not charged on Base, the fixed filter thresholds (TVL >= $10M, non-outlier APY), fetch-time pass-through from DefiLlama, and data staleness. The annotation idempotentHint=false is consistent with a per-call charge.

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 and return shape, then layers filters, freshness and billing. It is dense but nearly every clause carries decision-relevant information; the terms URL sentence is the only borderline item and is justified by paid-call obligations.

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 in structured data, the description fully enumerates the returned fields (project, chain, symbol, tvlUsd, apy, apyBase, apyReward, apyMean30d, stablecoin, exposure, ilRisk, poolId), the ordering rule, the result cap of 25, and the cost model. An agent has everything needed to call and interpret it.

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 baseline is 4; the description explicitly confirms 'no parameters', which matches the empty schema. No additional semantics are needed or offered.

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 and resource: current APY for stablecoin and DeFi pools. Scope is clear enough to pick it over generic siblings, but it never distinguishes itself from money_market_rates, which plausibly overlaps, so an agent must infer the boundary.

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 a concrete when-not-to-call rule ('data changes about every 1 h; calling more often returns the same values'), which usefully suppresses redundant paid calls. It stops short of naming alternatives or prerequisites beyond the implicit x402 payment requirement.

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