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 declares the tool is paid, names the price and accepted payment chains, states no account or API key is required, and that failed calls are not charged. Missing only rate limits or error/response semantics, which keeps it below 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-loaded with 'Paid.' followed by purpose, metrics, pricing and access terms in a few dense clauses with no filler. The trailing raw URL is marginally useful to an agent and is the only element that does not earn its place.

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 paid, zero-required-parameter read tool with no output schema, the description covers purpose, return metrics, cost, payment rails and endpoint. It does not describe result shape or pagination behavior, but the schema already documents the three filters, so the definition is nearly complete.

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 in the input schema. The description adds no extra meaning about these parameters (e.g., whether min_tvl_usd filters pools out entirely), 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?

The description states a specific verb and resource: live DeFi yields for the lagoon protocol, with the exact metrics returned (APY, TVL, 7d APY change) and the data source (DefiLlama). The protocol scope ('its pools across chains') clearly separates it from the buy_yields_chain_* and buy_yields_token_* sibling families.

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 paid-call context ($0.002 USDC on Base or Solana, no account, no API key) effectively says when this tool is usable, but there is no explicit when-to-use/when-not guidance relative to the large set of sibling yields tools. An agent must infer that this is the lagoon-protocol-specific drill-down versus the chain or token variants.

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