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

With no annotations supplied, the description carries the burden well: it discloses the paid model, exact price ($0.002 USDC on Base or Solana), no account/API key requirement, that failed calls are not charged, and the DefiLlama data source. What it omits is response shape or row/pagination behavior beyond the limit parameter documented in the schema.

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 the paid flag, then purpose, then pricing and access terms, ending with the endpoint URL. Dense and waste-free; the standalone fragment "Paid." is slightly abrupt but serves as a useful cost warning before anything else.

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-only lookup with a fully documented schema, the description covers the essential unknowns an agent would have: cost, payment rails, auth requirements, charge-on-failure policy, data provenance, and endpoint. Missing return-field layout is minor since no output schema exists but the described fields (APY, TVL, pool, protocol, chain) are effectively enumerated.

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. The description adds only the implied 'live pools' framing and the fact that results span protocols and chains, not any parameter-level meaning. 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?

"Where to earn yield on BTCB: live pools holding BTCB across protocols and chains, APY and TVL" gives a specific resource and the exact fields returned, which separates it from sibling token tools like buy_yields_token_wbtc or buy_yields_token_btc. It does not explicitly name an alternative, so it stops short of full sibling differentiation.

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 description establishes context (yield discovery on BTCB) and commercial terms, but never states when an agent should pick this over buy_yields_chain_*, buy_yields_protocol_*, or the wbtc/btc token variants. Usage is implied by the name rather than guided.

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