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

Annotations already declare read-only, idempotent, non-destructive behavior. The description adds useful behavioral context: these are standard rates, special/custom rates may be offered for larger amounts and are explained in the result, and ruble coverage depends on requesting a RUB pair.

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 front-loaded and well organized, moving from what the tool returns to usage examples and pair guidance. It is somewhat long but the length is largely justified by the rate types and RUB nuance.

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?

With no output schema, the description adequately explains the conceptual return content: online and cash buy/sell rates plus the NBG official rate, with special rates noted in the result. It is complete enough for an agent to call the tool correctly, though it omits any response-format detail.

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%, so the baseline is 3. The description adds meaningful pair semantics beyond the schema, especially the instruction to request a RUB pair for ruble-related questions; however, it adds little about the channel and language parameters beyond what the schema already documents.

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 a specific resource and scope: live FXHUB exchange rates for online bank transfer, cash exchange point, and NBG official rate. It is clear what the tool retrieves, but it does not explicitly differentiate itself from the sibling convert_currency tool.

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 concrete example questions and explains that an empty pair returns all pairs, plus a specific instruction to request a RUB pair for ruble-related questions. It does not explicitly say when to use convert_currency instead, but the context is otherwise clear.

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