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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful context the annotations lack: it is a paid call ($0.003 USDC) and it lists what data is returned. It does not disclose rate limits, error behavior, or payment fallback beyond what the schema mentions.

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 fragments, front-loading cost then purpose, with zero filler. Every clause (price, scope, returned fields) earns 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 two-parameter read-only tool with no output schema, the description covers what is returned and the pricing model. However, it leaves pool_id format unspecified and omits sibling routing, so an agent has enough to invoke it but not enough to confidently choose it over lookup_yields.

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 50%: api_key is documented in the schema, but pool_id has no schema description. The description partially compensates by clarifying that the id is a DefiLlama pool id, yet provides no format or example, and says nothing about api_key or payment beyond the cost header.

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 verb (lookup) and resource (one DeFi yield pool by DefiLlama pool id), and enumerates the returned fields (APY base/reward/30d mean, TVL, IL risk, risk score). It is distinguishable from lookup_yields by the singular 'one pool by id' framing, though it never names siblings explicitly.

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 gives no when-to-use guidance or exclusions; in particular it does not contrast itself with lookup_yields or free_defi_top_yields, which an agent must choose between. The only cue is implicit: you need a DefiLlama pool id, which narrows applicability but is not stated as guidance.

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