get_exchange_rate_history

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the agent knows this is a safe read. The description adds that the tool returns rates over a specified time period but does not disclose return format, grouping behavior, or any limitations. Given the annotation coverage, the description provides minimal but not rich additional behavioral context, warranting a 3.

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 a single concise sentence that fully conveys the tool's purpose without redundancy. Every word earns its place, and it is front-loaded with the key verb and resource.

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 is relatively simple with 5 parameters, full schema descriptions, and annotations indicating read-only behavior. The description explains the core functionality and is sufficient to guide invocation. However, it does not clarify the return shape (e.g., whether it returns a list of rates at intervals), which would be useful given no output schema. Still, overall completeness is good.

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?

The input schema covers all 5 parameters with descriptions and examples (e.g., 'source' as currency code, 'from'/'to' as ISO timestamps, 'group' as enum). The description itself adds no extra parameter meaning beyond what the schema already provides. With 100% schema coverage, 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 clearly states it retrieves historical exchange rates between two currencies over a time period. It uses a specific verb ('Get') and resource ('exchange rate history'), and the word 'historical' distinguishes it from the sibling tool get_exchange_rate, which likely returns the current rate.

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 implies when to use this tool (when historical rates are needed) through the word 'historical' and 'over a time period'. It does not explicitly mention alternatives, but the context of sibling tools (get_exchange_rate) makes the usage context clear. It lacks an explicit exclusion statement, so it falls short of a 5.

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