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

Annotations already declare this as a read-only, idempotent, non-destructive, open-world operation. The description adds useful behavioral context beyond that: it describes the returned content (rate, effective date, previous rate, decision history) and explains that the values are computed from the daily series. It does not cover update frequency or source limitations, but with annotations carrying the safety profile this is solid.

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, front-loaded sentence that begins with the resource and then lists the returned fields and the reason for the computation. Every clause contributes meaning: series ID, output fields, decision history, and the sibling comparison.

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?

Given zero parameters, no output schema, and annotations that already cover safety, the description is complete enough for correct invocation. It explains what the tool returns, how the values are derived, and why it is preferable to latest_observation for decision-date inference.

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, so the baseline is 4. The description appropriately focuses on the return semantics rather than inventing parameter behavior, and there are no gaps to compensate for.

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 names the specific resource (Riksbank's current policy rate), the exact series identifier (SECBREPOEFF), and the returned fields including effective dates and previous rate. It explicitly distinguishes itself from latest_observation by noting the caller does not have to infer the decision date from a bare {date, value}.

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 names the relevant alternative, latest_observation, and explains the condition under which this tool is preferable: when the caller needs policy-rate decision timing without inferring it from a bare observation. It does not spell out explicit when-not-to-use cases, but the alternative comparison gives clear context.

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