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

Goes well beyond the readOnlyHint/openWorldHint annotations by disclosing billing behavior (paid per successful call, x402, failed calls not charged), which materially affects how an agent should call it. It also flags the reference-data scope and absence of prices. It does not cover rate limits or result pagination beyond the limit 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?

Front-loaded with the core scope and the field list before the sibling routing, so the most important information comes first. It is dense but every clause carries content; the pricing tail is somewhat long for its weight but is genuinely actionable.

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 two-parameter reference-data tool with a full schema, full annotations and an output schema, the description covers scope, return fields, billing and alternatives, which is more than enough. Only return format/pagination detail is left implicit, and the output schema covers that.

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 coverage is 100% and both parameters are fully documented in the schema, so the baseline is 3. The description restates the filter's purpose ("filtered by a name or code fragment") and the returned fields but adds no syntax or matching detail beyond the schema, and never mentions limit.

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 verb+resource (currency list) plus the exact fields returned (code, name, minimum size) and explicitly negates the obvious confusion ("Reference data only; no prices"). It also names the two sibling tools it is not, so an agent can distinguish it without opening schemas.

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?

Explicitly routes the agent: use this for reference currency data, use finance_coinbase_exchange_products for trading products with status/minimum, and finance_coinbase_orderbook_candles for OHLCV at 1m/5m. Each alternative comes with the condition that selects it.

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