get_timeseries_rates

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

With no annotations, the description carries the full burden of behavioral disclosure. It explicitly states that days without published data are omitted, that a Business plan or higher is required, and that symbols can be used to reduce response size. These are concrete behavioral traits that go beyond the schema. It does not mention error handling, rate limits, or the exact response structure, but the disclosed behaviors are sufficient for basic selection and invocation.

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 four concise sentences with zero filler. It front-loads the primary purpose, then adds behavioral notes (omission of days, symbol filtering, plan requirement) in a logical order. Every sentence contributes new information without redundancy.

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 tool with four parameters, two required, and no output schema, the description covers the essential context: what it returns (daily rates keyed by date), the date range limit (366 days), the handling of missing data (omitted), and the plan requirement. It could be more explicit about the response format (e.g., whether each date maps to a rate object) and error behavior on exceeding the range, but the provided details are adequate for an agent to understand the tool's core behavior.

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 schema already describes all four parameters, so the baseline is 3. The description adds meaningful semantics: the 'range of at most 366 days' imposes a constraint on start_date and end_date not present in the schema, and 'Pass symbols to keep the response small' explains the purpose of the symbols parameter beyond its schema description. This adds value beyond the schema.

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 action ('Get daily exchange rates'), the resource ('exchange rates'), and the scope ('between two dates ... keyed by date'), making it distinct from siblings like get_latest_rates (single date) or get_pair_rate (single pair). The inclusion of the date-range specification and the note about omitting days without data further clarifies the tool's unique behavior.

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 does not explicitly reference alternative tools or state when to use this one instead of others. The note 'Requires Business plan or higher' is a prerequisite, not usage guidance, and 'Pass symbols to keep the response small' is a usage tip rather than a selection criterion. Usage is implied by the tool's name and purpose, but no exclusions or alternatives are provided.

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