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

With no annotations, the description usefully discloses the DefiLlama source, live nature of the data, exact charge, accepted payment networks, lack of account or API-key requirements, and that failed calls are not charged. It strongly implies a read-only lookup but does not explicitly state safety, response behavior, or payment mechanics.

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 logically ordered, leading with paid status and data content before cost, access requirements, failure billing, and endpoint. The phrase 'stablecoin live' is somewhat clipped, and the URL has limited selection value, but there is little substantive waste.

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 fixed, no-input endpoint, it covers nearly all practical invocation context: metrics, provider, price, payment rails, credentials, and failed-call charging. Because there is no output schema, the absence of response-shape and timestamp or freshness details leaves a modest completeness gap.

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 are no parameters to explain, so the zero-parameter baseline applies. The metric list and fixed PYUSD URL adequately clarify the scope of the parameterless request.

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 identifies the exact resource, PayPal USD (PYUSD), and enumerates the live metrics provided: peg-relative price, supply, supply changes, and per-chain supply. This clarifies that the tool retrieves data rather than purchases PYUSD, though it lacks an explicit retrieval verb and direct 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 live peg-and-supply focus implies that the tool is suitable for current PYUSD stablecoin monitoring. However, it gives no explicit routing guidance for generic price questions versus buy_crypto_price, grouped stablecoin checks, or buy_yields_token_pyusd.

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