Rate cache status

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

No annotations are provided, so the description carries the full burden. It states the tool is read-only, explains that it reports freshness and refresh timing, and discloses the quarantine behavior for a cache that no longer parses. It does not cover error cases or output format, but for a simple read-only report this is reasonable coverage.

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?

Three sentences, with the primary purpose front-loaded in the first line. Every sentence earns its place: what is reported, read-only nature, the use case, and what happens when a cache fails to parse. No fluff.

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 parameter-less, no-output-schema status tool, the description covers everything an agent needs: resource, contents, read-only behavior, refresh insight, and operational guidance. Nothing required to call it is missing.

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 input schema is empty, so there are no parameters to document. Per the calibration rules, a 0-parameter tool earns a baseline of 4. The description adds semantic value by indicating what the report contains, which is enough for this no-argument tool.

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 verb ('Report the ECB rate cache') and the resource, then lists precisely what it reports: which dates are held, their age, and when they refresh. The 'Reads only' line plus the cache-status focus differentiates it from sibling conversion tools like rates_latest or fx_rates_for, even though no sibling is named.

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?

Clearly tells the agent when to use the tool: 'Check it before trusting a rate after a time offline.' This gives local context that ties to an actual decision point. It does not explicitly name alternatives or give when-not-to-use conditions, but the practical guidance is strong enough.

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