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

With no annotations, the description does real work: it discloses that the call is paid, the exact price and accepted chains, that no auth is needed, that failures are not charged, and that data originates from DefiLlama. That failure/charging semantics is exactly the kind of behavior an agent cannot infer elsewhere. It omits freshness/latency and rate-limit behavior.

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-loads 'Paid.' so cost is seen before any invocation decision, then purpose, inventory of metrics, source, price/rail, auth, failure policy, endpoint. Telegraphic but every fragment carries load, and no sentence is redundant.

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-param, no-output-schema tool, the description covers what an agent needs: what data returns, what it costs, how to pay, and that failures are free. Return shape is described by metric names rather than structure, which is the main residual 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?

The tool takes zero parameters, so there is no parameter meaning to convey; baseline 4 applies. Nothing in the description is needed to explain inputs, and it does not waste words pretending otherwise.

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 the specific resource (SoFiUSD/SOFID stablecoin) and enumerates exactly what comes back: price vs peg, supply, 1d/7d/30d supply change, per-chain supply. The ticker itself is what distinguishes it from the ~30 sibling buy_stable_* tools, so differentiation is implicit rather than stated.

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?

Gives access prerequisites (no account, no API key) and the payment rail ($0.01 USDC on Base or Solana), which is decision-relevant. But it never says when an agent should call this versus a sibling like buy_stable_usdc or a broader stablecoin listing, and offers no exclusions or fallback.

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