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

Annotations already mark it read-only and open-world. Beyond that, the description discloses the 20-pool result cap, that APY is an estimate rather than a guaranteed return, and the paid-per-successful-call x402 billing model (failed calls free). Those are useful behavioral details an agent cannot get from annotations or 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?

Three efficiently loaded sentences: data returned first, filters and result cap second, data-quality caveat and pricing third. Every sentence carries distinct information and there is no repetition.

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 handling return shape and annotations covering safety, the description is nearly complete: it covers fields returned, filters, result limit, data reliability, and payment. The only minor gap is that pagination or behavior beyond the 20-pool cap is not addressed.

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% and each parameter has examples (Ethereum/Base/Arbitrum, USDC/WETH-USDC, aave-v3). The description only restates the filterable fields ('project, chain and symbol') without adding syntax, defaults, or matching behavior beyond the schema, so baseline 3 applies.

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 the specific resource (DeFi pool APY, TVL, APY change, impermanent-loss estimate) and the source (DefiLlama), so an agent knows exactly what data it returns. It doesn't name or distinguish itself from close siblings like crypto_defillama_tvl_oracle, crypto_defillama_stablecoins, or finance_defirate_yields, leaving overlap implicit.

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?

The filtering options ('Filter by project, chain and symbol') and the 'up to 20 pools by TVL' cap imply the intended usage, but there is no explicit when-to-use guidance and no alternatives or exclusions mentioned. An agent must infer that this is for yield/TVL lookups rather than, say, stablecoin supply or protocol TVL.

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