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

Annotations already declare the operation as a read-only, closed-world lookup, so the safety profile is covered. The description adds a genuinely useful trait — the $0.002 USDC paid call — but says nothing about rate limits, data freshness, or what happens when payment/credits are absent.

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 terse fragments, cost first then payload, with zero filler. Every clause conveys an actionable fact.

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?

With no output schema, the description correctly enumerates the returned fields, which is the key piece of missing context, and the schema handles auth/payment. Only usage routing and data-source/freshness notes are absent.

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%: 'q' is documented as a DefiLlama slug/name with an example, and 'api_key' explains the prepaid vs x402 payment path. The description adds nothing about parameters, 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?

The description names a specific resource and its exact payload: one DeFi protocol's TVL, 1d/7d change, category, chains and market cap. This inherently separates it from lookup_coin, lookup_pool and lookup_yields, though it never names those 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?

There is no guidance on when to choose this over lookup_coin, lookup_pool, lookup_yields or the free_* variants, and no stated prerequisites or failure conditions. The agent must infer routing purely from the resource noun.

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