rate_timeseries

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

With no annotations, the description carries the full burden and does well: it discloses the per-working-day granularity (implying holiday gaps), the min/max/average aggregation, and two refusal conditions that never reach upstream. It stops short of stating the configured maximum range length or whether errors are returned as structured failures.

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?

Front-loaded with the resource definition, then returns, then failure behavior — a logical order with no filler. Length is appropriate for the amount of information conveyed, though the last clause could be tightened.

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?

An output schema exists, yet the description helpfully pre-summarizes the response shape (per-day points plus aggregates), and it covers the invalid-input paths. The only meaningful omission is the actual value of the configured maximum range, so the agent cannot self-check before calling.

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 all four parameters including ISO 4217 formatting and the 366-day constraint are already documented. The description only adds the framing that base/symbol form 'one currency pair', which is a marginal gain over the schema baseline.

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?

Names a specific resource and scope: the ECB reference rate for one currency pair over a date range. An agent can distinguish it from latest_rates and historical_rate by the range framing, but the description never names those siblings to make the boundary explicit.

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?

Usage is implied by 'across a date range' — use this instead of a single-point lookup when a series is wanted. However, no alternative is named and no when-not-to-use condition is given beyond the internal validation rules (range too long, start after end), which are error handling rather than tool selection guidance.

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