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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, covering the safety profile. The description adds useful behavioral context: it returns a flat array of lowercase strings, has exactly 63 entries, and takes no parameters. It doesn't contradict the annotations and provides sufficient detail for a simple read-only list tool.

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 three sentences, each earning its place: the first defines the resource, the second specifies the output format and parameter absence, and the third gives usage guidance and an alternative. No fluff, and key information is front-loaded.

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 no-parameter tool with an output schema (provided separately), the description is complete: it states what is returned, the count, examples, when to use it, and the alternative for a related purpose. An agent can correctly decide to call this tool without needing additional details.

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 has zero parameters, and the schema shows an empty object. The description explicitly states 'takes no parameters', which reinforces the schema. Since there are no parameters to explain, the description appropriately focuses on the output and usage context.

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 states that the tool returns the list of quote currencies accepted by the vs_currency parameter of other CoinGecko tools, and explicitly distinguishes it from the coin-side list tool (get_coingecko_coins_list). It names specific currencies and the return format, leaving no ambiguity about what the tool does.

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?

It provides explicit guidance: call this before using a non-obvious quote currency rather than guessing, and names the sibling tool to use for coin identifiers. This clearly defines when to use this tool versus alternatives.

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