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

Annotations already declare readOnlyHint/idempotentHint, and the description adds that the call is 'no auth' and sourced from 'Norges Bank SDMX IR dataflow.' It also discloses the return shape as '{date, rate} pairs sorted ascending,' which is beyond the schema. No other behavioral caveats are needed for this read-only tool.

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 front-loaded with the core action, then lists selection dimensions, return shape, use-case, and data source in short sentences. Each sentence carries distinct information, though the parameter list partially duplicates schema documentation.

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?

The description provides the essential operational context: no auth required, the source dataflow, return format, and intended use cases. With an output schema present and all parameters optional with documented defaults, nothing critical is missing for an agent to call this 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?

Input schema covers 100% of parameter docs, so baseline is 3. The description merely restates the enum values (SD/OL/RR, B/M/A) and date-range selection that are already documented in the schema, adding no new parameter-level meaning.

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?

States a specific verb ('Retrieve'), resource ('historical time series of Norges Bank key policy interest rates'), and enumerates the exact selectable dimensions (rate type, frequency, date range). This is clearly distinct from sibling tools like norgesbank.rates.current (current rates) and norgesbank.fx.history (exchange rates).

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?

Gives context by stating it is 'Useful for monetary-policy research, macro models, or comparing Norway's rate cycle against other central banks.' It does not explicitly name alternatives or list when-not-to-use cases, but the 'historical' scope and mention of Norway's cycle provide clear context for selection.

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