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

Annotations already declare a safe read against an open world, and the description adds genuinely non-obvious behavior: this is a pay-per-call endpoint billed in x402 USDC on Base, and a missing payment returns a payment challenge rather than data. That failure-mode disclosure is valuable. It does not cover freshness/caching or rate limits, so it falls short of a 5.

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 sentences, zero waste: the resource and source come first, the payment mechanics second. Every clause earns its place.

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?

An output schema exists, so return values need no explanation, and the description covers purpose plus the billing/failure behavior an agent must handle. It leaves the 'stablecoin-only' scoping and any freshness guarantees unstated, which is a minor gap for a simple optional-param listing tool.

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 coverage is 100%, so the schema already documents chain, limit, and minTvl with formats and defaults. The description adds no parameter-level meaning beyond that, so the 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?

States a specific resource (DeFi stablecoin pool APYs) and its data source (DeFiLlama), which is enough to distinguish it from the TVL, funding, and edge siblings that cover other DeFi metrics. It does not explicitly name those siblings, so differentiation requires the agent to infer from the resource noun.

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 implied by the resource ('get pool yields'), and the payment precondition is stated, but there is no guidance on when to prefer this over tvl or funding, nor any exclusions. The agent must infer the use case.

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