get_historical_exchange_rates

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

Annotations indicate read-only and open-world operations, which the description aligns with by describing a data retrieval function. The description adds valuable behavioral context beyond annotations, such as fallback behavior ('closest date before' if unavailable) and default behavior when symbols are omitted, enhancing transparency without contradiction.

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 well-structured and concise, with four sentences that each add essential information (purpose, fallback behavior, input requirements, and filtering logic). It is front-loaded with the main purpose and avoids redundancy, making it efficient for quick understanding.

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?

Given the tool's moderate complexity (5 parameters, no output schema), the description is largely complete, covering purpose, behavior, and input logic. However, it lacks details on output format (e.g., structure of returned rates) and error handling, which could aid the agent despite the absence of an output schema.

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%, so the schema fully documents all parameters. The description adds minimal semantic context beyond the schema, such as clarifying that symbols filter results and are optional, but does not provide significant additional meaning. This meets the baseline for high schema coverage.

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's purpose with specific verbs ('Returns historical exchange rates') and resources ('for a specific date or date range'). It distinguishes from siblings like 'get_latest_exchange_rates' by specifying historical data and from 'convert_currency_specific_date' by focusing on rate retrieval rather than conversion.

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 provides clear context for when to use this tool (for historical rates with date/range inputs and optional currency filtering). However, it does not explicitly mention when not to use it or name specific alternatives among the siblings (e.g., 'get_latest_exchange_rates' for current rates), leaving some ambiguity.

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