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

Annotations already declare read-only and idempotent behavior, and the description adds beyond that: the uppercase case-sensitivity trap, the misleading HTTP 404 'No data found' result, and the list of valid bank codes. This extra behavioral context is highly valuable and goes well beyond the 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?

The description is compact and front-loaded: it opens with the data shape, moves to required parameter behavior, and then gives the critical edge case. The valid-code list slightly overlaps the enum, but it earns its place by supporting the actionable uppercase warning.

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?

With annotations covering safety and an output schema present, the remaining needs—required parameter, valid codes, case sensitivity, date binding, and the snapshot alternative—are all addressed. Nothing essential is missing for an agent to call this tool correctly.

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 the schema already documents the parameters. The description still adds meaning by explaining the relationship between `bank`, `start_date`, and `end_date`, and by emphasizing the case-sensitivity warning that affects how the agent interprets failures.

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 states a specific operation: retrieving one central bank's policy rate over time, and names the exact output shape (`interest_rates` array of `bank`, `name`, `date` and `rate`). It also distinguishes the tool from its sibling `get_financial_macro_interest_rates_snapshot` by noting the snapshot lists valid codes, so an agent can tell them apart.

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?

It clearly says `bank` is required, explains the date-bounding relationship, and directs the user to the snapshot tool for listing valid codes. It does not explicitly state when not to use this tool versus other financial siblings, but the context is strong enough for correct selection.

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