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

With no annotations, the description carries the full burden and does well: it discloses that the call is paid ($0.01 USDC on Base or Solana), needs no account or API key, is not charged on failure, and that data comes from DefiLlama. It stops short of stating rate limits, response shape, or what an error looks like, so not 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?

A single tight paragraph with no filler; cost and payment rails are front-loaded ahead of the data description, which is the right priority for a paid tool. The trailing raw URL is slightly awkward but functionally useful.

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 zero-required-parameter read tool with no output schema, the description covers what is returned (pools with APY, TVL, 7d change), the source, the cost, the payment methods, and the failure-charge policy — everything an agent needs to decide and call correctly.

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% and all three parameters (sort, limit, min_tvl_usd) already carry inline descriptions with defaults. The description adds no parameter-level 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?

States a specific resource and scope: 'Live DeFi yields for crvusd: its pools across chains with APY, TVL, 7d APY change (DefiLlama data)'. That is clearly distinct from a generic price tool. It does not explicitly distinguish itself from near-neighbors like buy_yields_token_crvusd or buy_stable_crvusd, which is the only thing keeping it from 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 the data description (protocol-level pool yields for crvusd) but there is no explicit when-to-use or when-not-to-use guidance, and no routing to the token-level or stablecoin sibling tools that cover overlapping ground. The agent must infer the distinction from the tool name alone.

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