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 ($0.002 USDC on Base or Solana), that no account or API key is needed, that failed calls are not charged, and the underlying data source and endpoint. It does not describe the response shape, pagination, or latency, 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 paid marker, then the purpose, then commercial terms in short fragments with no filler. The staccato style is efficient, though the pricing and URL lines could be slightly tighter.

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 tool with no output schema, the description covers what data comes back (APY, TVL, 7d change), where it comes from, and how billing works. Return structure and default row shaping are left to the schema, which is acceptable here.

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, and min_tvl_usd are already documented by the schema. The description adds no additional meaning about these controls, 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 the navi-lending protocol, with the returned fields (APY, TVL, 7d APY change) and the data source (DefiLlama). The protocol name in the tool name plus description is enough to separate it from the many buy_yields_protocol_* siblings, though it never explicitly says so.

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 only implied — an agent infers it should call this when it wants navi-lending pool yields. There is no statement of when to prefer buy_yields_chain_* or buy_yields_token_* instead, and no preconditions beyond the payment note.

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