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

With no annotations, the description carries the behavioral burden and does well: it discloses the free-tier delay, paid-tier coverage, confidence classes, citation behavior, and what happens when a country does not publish a rung independently. It stops short of stating read-only behavior, rate limits, or error handling explicitly.

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 definition is dense but front-loaded, opening with the core concept and then adding access-tier context. The long first sentence is information-rich and every element is relevant, though it is close to being overloaded.

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?

An output schema exists, so the description need not explain return values in full, yet it still covers the key output components and access tiers. It lacks explicit routing guidance versus sibling tools and auth/error details, which keeps it from a 5.

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 100%, and the schema already documents both the required ISO 4217 currency code and the optional citation language. The description adds no syntax or format details beyond what the schema provides, so baseline 3 is appropriate.

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 states exactly what the tool returns: the full ladder of rates for one currency on its latest day, including specific rungs, gaps, trends, widening signal, and citation. The enumerated rungs and derived metrics make its scope unmistakable and distinguish it from single-rate siblings such as get_street_rate or get_official_vs_street, even without naming them explicitly.

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 gives useful context that this covers the latest day and explains free versus paid access levels. However, it does not explicitly say when to choose this tool over related siblings like get_street_rate, get_official_vs_street, or get_rate_history, so usage is implied rather than guided.

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