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

With no annotations provided, the description carries the full burden of behavioral disclosure. It does not state whether the tool returns current values, historical series, or a snapshot, nor does it mention update frequency, data source, or any limitations. The agent is left to infer the tool's behavior from the rate names alone.

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 a single, well-structured sentence with a colon introducing a comma-separated list of rates. It is concise and free of filler, though the lack of a verb makes it feel more like a label than an action statement.

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 simple no-parameter tool, the description conveys the core content (which rates are covered) but omits important context such as whether values are current or historical, units (percent vs basis points), or how this relates to other ECB tools. It is minimally viable but leaves clear gaps.

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 tool has zero parameters and the input schema is an empty object with 100% coverage. The baseline for zero-parameter tools is 4, and the description adds no parameter-related ambiguity. No additional param explanation is needed.

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 identifies the tool as providing ECB interest rates and enumerates specific rate types (Main Refinancing, Deposit Facility, Marginal Lending, EURIBOR, Euro Short-Term Rate). While it lacks an explicit verb like 'returns' or 'lists', the resource is highly specific and distinguishes it from sibling tools such as ecb_yields or ecb_fx.

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?

There is no guidance on when to use this tool versus alternatives like fed_rates, ecb_yields, or ecb_dashboard. The description simply lists the available rates without any context or decision criteria.

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