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

With no annotations at all, the description carries the full burden and covers the things that actually matter: it is a paid call, the price ($0.01 USDC on Base or Solana), the data source (DefiLlama), that no account or API key is needed, and that failed calls are not charged. Cost, auth, and failure semantics are exactly the preconditions an agent needs before spending money.

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 'Paid.' — the most decision-relevant fact — followed by scope, returned fields, pricing, auth, and endpoint in five tight sentences. Nothing is padding.

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 3-optional-param read tool with no output schema, the description gives the return field set (base/reward APY, TVL, 7d APY change), data source, and full payment preconditions. Only minor gaps remain, such as response format and whether results are capped beyond the limit parameter.

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 sort/limit/min_tvl_usd are already documented. The description restates the sort modes (TVL or APY) and the returned fields but adds no constraints, ranges, or defaults 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?

States a specific verb+resource+scope: live DeFi yields on the Stable chain, ranked by TVL or APY. The chain qualifier distinguishes it cleanly from the ~350 sibling tools (buy_yields_chain_base, buy_yields_protocol_*, buy_yields_token_*) without needing the schema.

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 chain scope plus 'top pools by TVL or APY' makes clear this is the chain-level ranked-pool lookup rather than a protocol- or token-specific one. It does not name an explicit alternative or say when to prefer buy_yields_protocol_* / buy_yields_token_* instead, so no exclusions are stated.

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