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 does well: it discloses pricing, payment rails, no-auth access, that failed calls are not charged (safe to retry), the data source (DefiLlama), and freshness ('Live'). It omits rate limits and response/pagination shape, keeping it 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?

Payment notice is front-loaded, followed by the data payload and access terms, in a compact block with no filler. The URL at the end is mildly redundant but aids debugging.

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 simple read-only, zero-required-parameter tool with no output schema, cost, data source, freshness, and returned metrics cover nearly everything an agent needs. Explicit return field structure or pagination behavior is the only notable gap.

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 already documented in the schema. The description adds no filtering or ordering semantics 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 (live DeFi yields for pendle-v2) and enumerates the returned fields (APY, TVL, 7d APY change). 'its pools across chains' implicitly distinguishes it from chain- and token-scoped siblings, but no sibling is named explicitly.

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?

Gives payment context ($0.01 USDC on Base or Solana, no account or API key), which tells the agent the cost and prerequisites, but offers no when-to-use guidance versus sibling tools like buy_yields_chain_* or buy_yields_top, and no explicit exclusions.

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