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

With no annotations, the description carries the full burden and does substantial work: it discloses that the call is paid ($0.01 USDC on Base or Solana), requires no account or API key, is not charged on failure, and sources data from DefiLlama. It does not describe the response shape or whether results are paginated beyond the limit parameter.

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?

Two tight sentences with zero filler: resource and scope first, then payment mechanics and the endpoint URL. Every clause (price, chain, auth, refund policy) is information an agent needs before calling a paid endpoint.

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 paid read endpoint with no output schema and no annotations, the description covers the essentials: what data comes back (pools with APY and TVL), cost, payment rails, auth, and failure billing. The only gap is return structure/pagination detail, which is minor given the fixed token scope.

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 fully documented with defaults and ranges. The description only indirectly gestures at the sortable fields by naming 'APY and TVL'; it adds no filtering or ordering semantics beyond the schema, so 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 pools holding USTB across protocols and chains, APY and TVL'. The 'across protocols and chains' phrasing implicitly separates it from the buy_yields_protocol_* and buy_yields_chain_* siblings, though it never names them. The token-specific suffix pattern makes the resource unambiguous.

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 resource (use this when you want yield opportunities for USTB), but there is no explicit when-to-use or when-not guidance. In particular it never routes the agent away from the near-duplicate sibling buy_yields_protocol_invesco-ustb or explains how this differs from the generic buy_yields_stablecoins endpoint.

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