Currency Time Series

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

Annotations already declare readOnlyHint, destructiveHint, idempotentHint, and openWorldHint. The description adds beyond that: it describes the return structure ('historicalRatesList array') and clarifies the use case (charting, analyzing trends). It also notes the 1-year limit and default behavior of endDate, which are not in annotations.

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?

Three sentences, no filler. The first sentence captures the core purpose, the second adds structural detail about the return format, and the third handles parameters. Every sentence earns its 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?

Despite no output schema, the description explains the return format and key constraints. For a time series tool with 4 parameters and a clear domain, this covers what an agent needs to know. Sibling tools are many but clearly distinguished by name.

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 coverage is 100%, so baseline is 3. The description adds significant value: it implies startDate is required, explains endDate defaults, mentions that omitting symbols returns all rates, and advises using currency_symbols for valid codes. This extra guidance meaningfully aids correct invocation.

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 'Retrieve historical exchange rates day-by-day across a custom date range,' specifying the verb (retrieve), resource (historical exchange rates), and unique scope (day-by-day range). This distinguishes it from siblings like currency_historical_rates (single date) and currency_time_series is the right tool for multi-day periods.

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 context on required and default parameters ('startDate is required; endDate defaults to yesterday') and a constraint ('Max interval supported is 1 year'). However, it does not explicitly state when to avoid this tool or point to dedicated siblings like currency_historical_rates for single dates or currency_fluctuation for changes.

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