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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds the default currency behavior ('BRL por padrão'), which is useful, but does not disclose other behavioral traits such as error handling, rate limits, or response structure. With annotations covering the core safety, the added value is moderate.

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 a single, concise sentence that front-loads the core function. It contains no redundant information and is easily parsed by an agent.

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 read-only tool with two parameters and strong annotations, the description covers the essential purpose and default behavior. It does not mention return format or alternative tools, but given the low complexity and annotation coverage, it is adequately complete for basic invocation.

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?

Schema description coverage is 0%, so the description must compensate. It provides meaning for both parameters: 'coins' are cryptocurrency symbols (BTC, ETH), and 'currency' is the chosen quote currency with a default (BRL). This adds substantial semantic value beyond the plain schema, though it does not specify formatting details like uppercase or currency codes.

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 the tool provides cryptocurrency quotes ('Cotação de criptomoedas') with examples (BTC, ETH) and the currency selection. It identifies a specific verb+resource, but does not explicitly differentiate from sibling tools like mercado_quote, so it lacks direct sibling distinction.

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 description gives no guidance on when to use this tool versus alternatives. It does not mention when not to use it or provide context about sibling tools, leaving the agent without decision support for tool selection.

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