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

With no annotations, the description must carry the behavioral burden, and it does more than most: it discloses the paid model ($0.01 USDC on Base or Solana), that no account or API key is needed, that failed calls are not charged, and the upstream data source (DefiLlama). It does not cover data freshness/staleness, rate limits, or result pagination behavior, which keeps it from 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?

Front-loads the key gating fact ('Paid.') before the value proposition, then packs scope, fields, price, auth model, billing policy, and endpoint URL into three sentences with no filler. Nothing restates the tool name uselessly.

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?

No output schema exists, but the description names the returned fields (APY, TVL, 7d change) and where the data comes from, plus payment and failure semantics. Missing only secondary operational details like rate limits and pagination, which are minor for a single read-only query 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 description coverage is 100% and all three parameters (sort, limit, min_tvl_usd) carry inline descriptions with defaults and ranges. The prose adds no parameter meaning beyond the schema, 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?

The description states a specific resource ('Live DeFi yields for frax-ether') and enumerates returned fields (pools across chains, APY, TVL, 7d APY change, DefiLlama source). That is enough to separate it from chain-level or token-level yield siblings. It stops short of explicitly contrasting itself with any named sibling, so it lands just under 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?

Usage is implied by scope: call this when you want yield pools for the frax-ether protocol. There is no explicit when-to-use statement, no when-not, and no pointer to alternatives such as buy_yields_protocol_frax, buy_yields_chain_*, or buy_yields_top for broader coverage. Given ~300 sibling protocol endpoints, an explicit routing sentence would materially help.

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