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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds meaningful behavioral context beyond those: the cache can become unparsable and 'quarantined and named', and the tool reports refresh timing. This enriches the agent's understanding of cache health without contradicting annotations.

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 three sentences with no wasted words. It front-loads the primary purpose, then adds the when-to-use hint and the quarantine caveat. Every sentence earns its place.

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 zero-parameter, read-only status tool, the description is complete: it states what is reported, when to check it, and a key failure behavior. No output schema exists, but the description does not need to enumerate return fields for an agent to invoke 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?

The tool has zero parameters and the schema is empty, so there are no parameter semantics to clarify. Per baseline for zero-parameter tools, a score of 4 is appropriate; the description correctly focuses on the tool's no-input status behavior.

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?

Description uses a specific verb ('Report') and resource ('ECB rate cache'), and details exactly what is reported: held dates, age, and refresh timing. It clearly distinguishes this cache-status tool from sibling rate-conversion and rate-query tools like rates_latest and rate_history.

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 gives explicit context for when to use the tool: 'Check it before trusting a rate after time offline.' It also explains the quarantine behavior. It does not explicitly state when not to use it or name alternatives, but the usage trigger is clear enough for an agent to decide.

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