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

With no annotations, the description carries the full behavioral burden, and it discloses that this is paid ($0.002 USDC on Base or Solana), that no account or API key is needed, and that failed calls are not charged. It gives the data source and freshness (live pools, DefiLlama) and the endpoint URL. It does not describe the response shape or rate limits, which is a minor gap given a paid endpoint.

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?

A compact, front-loaded block: purpose first, then price, payment rails, auth, billing policy and URL. Every clause carries information. The '$0.002 USDC on Base or Solana' construction and the trailing bare URL are slightly terse but not wasteful.

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 a three-optional-parameter read with no output schema, the definition covers what is queried, the data source, cost and billing behavior. It does not sketch the returned fields (pool, chain, protocol, APY, TVL), which would help an agent know what to expect from the paid call, but nothing essential to calling it is missing.

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 sort, limit and min_tvl_usd are fully documented in the schema, including defaults. The description adds no parameter meaning beyond the schema, which is the expected baseline when the schema does the work.

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 names a specific verb and resource: live pools holding ETH where you can earn yield, with APY and TVL from DefiLlama. An agent can tell this is an ETH-token yield query rather than a chain, protocol or stablecoin yield query. It doesn't differentiate price action for ETH or wrapped ETH (buy_yields_token_weth), but the required endpoint is clearly described.

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 scope, but the description never states when to use it instead of its close siblings (buy_yields_chain_ethereum, buy_yields_protocol_aave-v3, buy_yields_token_weth). It also omits prerequisites for the agent other than paying: there is no account or API key, which it does state.

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