get_historical_rates

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

No annotations are provided, so the description carries the burden of disclosing behavioral context. It adds the 'Requires Pro plan or higher' prerequisite and enforces the YYYY-MM-DD date format, but it does not mention error behavior for invalid dates, response shape, or any side-effect/read-only reassurance.

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?

Two short sentences with no filler, and the core purpose is front-loaded. The date format and plan requirement are relevant extras that earn their place.

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?

For a low-complexity tool with three well-documented parameters, the core purpose and access prerequisite are covered. However, with no output schema and no annotations, the description omits details about what is returned, how errors are signaled, and which sibling tools cover other time ranges.

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 already documents base, date, and symbols. The description only restates the date format and adds no additional meaning about filtering behavior, defaults, or edge cases, which matches the baseline of 3.

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 uses a specific verb ('Get'), a clear resource ('exchange rates'), and a precise scope ('specific past date'). This distinguishes it from sibling tools like get_latest_rates and get_timeseries_rates, which target different time ranges.

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 phrase 'specific past date' implies this is for one historical date rather than a range or the latest rates, but no alternatives are named and no when-not-to-use guidance is given. The Pro plan requirement is a constraint, not a usage heuristic.

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