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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive behavior. The description adds valuable context beyond that: no authentication required, business-day spot rates, SDMX REST API source, open government licence, and unlimited use. This gives an agent confidence about access constraints and data provenance.

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: the first sentence states the core purpose and scope, and each subsequent sentence adds a distinct fact (filtering, authentication, data source, licensing). There is minor repetition of Norges Bank/SDMX, but no waste that would impair agent comprehension.

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 the output schema exists, annotations cover safety, and the only parameter is fully documented, the description covers everything else an agent needs: data source, freshness, base currency, filtering behavior, authentication, and licensing. It is complete for a simple read-only latest-rates tool.

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 schema already fully documents the single currencies parameter at 100% coverage, including comma-separated ISO codes and the empty-means-all behavior. The description reinforces this with an example ("USD,EUR,GBP"), which is helpful but does not add substantial new meaning beyond the schema.

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 opens with a specific verb and resource: "Get the latest official foreign-exchange rates published by Norges Bank." It further distinguishes the tool by scope (up to 41 currencies), base currency (NOK), and recency (latest, business-day spot rates), making it easy to separate from norgesbank.fx.history and related FX tools.

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?

The description clearly establishes that this tool is for the latest official Norges Bank FX snapshot and explains how to filter with the optional currencies parameter. It does not explicitly name an alternative for historical data, so it stops short of full when-not-to-use routing, but the 'latest' framing gives clear usage context.

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