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

Annotations already declare readOnlyHint and openWorldHint, so the description's main added value is disclosing the $0.01 per-call cost and the USDC-on-Base payment mechanism via x402. This is useful operational context beyond annotations and does not contradict them.

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?

The description is compact and front-loaded: first sentence states what it returns, second gives the use case, third covers cost/payment. Every sentence earns its place and no filler is present.

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 task with one optional parameter, the description is nearly complete: it explains the output metrics, the purpose, and the cost/payment context. It could add a note about data source freshness, but the schema's DeFiLlama reference and the read-only annotation cover most needs.

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?

There is only one optional parameter and the schema already documents it fully (DeFiLlama protocol identifier, default aave, example aave). The description adds no parameter-specific meaning beyond what the schema provides, so the baseline of 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 clearly identifies the resource (DeFi protocol) and the returned data: TVL in USD plus 24h and 7d changes. It is distinguishable from sibling tools like precio, saldo, and velas, though it does not explicitly name them. A slightly more direct action verb would make it fully explicit.

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 phrase 'measure of a protocol's size and health before you interact with it' gives a clear use context for when to call the tool. It does not mention exclusions or alternative siblings, so it stops short of full guidance.

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