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

Beyond readOnlyHint/destructiveHint, the description discloses the data source (DefiLlama), the auth/cost model ($0.01/call via x402 USDC or card key, first 25 free, failed calls free), and explicitly explains why idempotentHint=false — 'each call is charged, so repeats are not free.' It also names the returned fields, which matters since there is no output schema.

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-loaded with what the tool returns, then filters, then a use case, then cost/auth. Dense but nearly every clause carries information; only the 'Not investment advice' line is boilerplate that could be dropped.

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?

For an 11-parameter, zero-required, read-only tool with no output schema, the description covers data source, return fields, filter surface, default behavior implied by the schema, and the billing/auth model. An agent has everything needed to call it correctly and understand the cost implication of repeating a call.

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?

Schema description coverage is 100%, so the schema already documents every one of the 11 filters including defaults (minTvl 1M, maxApy 1000, limit 20). The description mostly restates the same filter set and sort options rather than adding syntax or interaction semantics, so the baseline 3 applies; the chain=Base example is a small bonus.

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 — 'the best DeFi yields now across ~15,000 lending, staking, LP and vault pools' — and enumerates the returned fields (APY base/reward, 30-day mean, TVL, stablecoin flag, IL risk). The word 'now' implicitly separates it from the sibling defi_yield_history, but no sibling is named explicitly, which keeps it just short of a 5.

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?

'Use to find where to earn yield on a token or stablecoin' gives a clear triggering scenario, and the example (chain=Base) shows a concrete invocation. However, it never names an alternative tool (defi_yield_history, liquidity_pool_audit) or states when not to use it, so routing is left partly to inference.

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