history_rates

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

With no annotations, the description carries the full burden. It discloses the date range limit and the need for repeated calls for longer ranges. However, it does not describe the return format (though an output schema exists), potential errors, or whether the data is read-only. The mutation status is implied as read because it is a GET-like operation.

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 two sentences, front-loading the purpose and then immediately adding the critical constraint. Every word serves a purpose, no redundancy or fluff.

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?

The tool has 3 required parameters, no parameter descriptions, no annotations, and an output schema exists but is not referenced. The description covers the core purpose and a key limitation, but omits parameter semantics and return value context. It is adequate but feels incomplete for a new user.

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 only mentions 'single currency', hinting that char_code is a currency code, but provides no format or examples. It offers no additional meaning for date_from and date_to beyond what schema names imply (start and end dates).

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 does with a specific verb ('Get'), resource ('exchange-rate series'), and scope ('official CBR', 'single currency', 'between two dates inclusive'). It clearly distinguishes from siblings like 'get_rate' (likely for a single rate) by emphasizing a series of rates over a date range.

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 explicitly mentions the 366-day cap and instructs to call repeatedly for longer windows. This provides clear when-to-use and when-not-to-use guidance. However, it does not explicitly mention alternatives or compare to sibling tools, such as suggesting 'get_rate' for a single day.

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