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

With no annotations, the description carries the full burden, and it does: cost ($0.002 USDC), accepted payment chains (Base or Solana), no authentication required, and no charge on failure. It also discloses the data methodology (median of two named exchanges with each source shown), which the agent cannot infer from any structured field.

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?

Six terse fragments, front-loaded with the paid flag, then what is returned, then price and payment rails, then access terms, then the URL. Nothing is redundant, and the telegraphic style suits a high-volume catalog.

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-parameter paid endpoint with no output schema, the description covers the response contents, the cost, the payment options, the auth model, and the failure policy. Little else would change an agent's decision to call it.

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 the baseline is 4. The description correctly implies no inputs are needed and spends its words on scope, cost, and output content instead of inventing parameter detail.

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 resource and scope: a storage-token basket (FIL, AR, STORJ, SC) USD median of Coinbase and Kraken. This clearly distinguishes it from the single-coin siblings buy_coin_FIL/buy_coin_AR and from other buy_cp_* baskets.

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?

Implies at least three usage conditions: this is a paid call, it needs no account or API key, and failed calls are free, so an agent knows it can attempt it without credentials. It never names alternatives (e.g. buy_coin_FIL for a single asset or buy_crypto_price for a spot price), so sibling routing is left implicit.

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