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

Annotations already declare readOnlyHint, idempotentHint, closed-world, and non-destructive, so the safety profile is covered. The description adds one useful behavioral fact — that output is a re-expression of the same snapshot (so it is consistent with get_rates, not freshly fetched) — but says nothing about the response shape, unsupported-currency behavior, or which date is used when date is omitted.

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?

Eight words with no filler and the key concept front-loaded. It is efficient, though the clipped fragment style trades a little grammatical clarity (no verb) for brevity.

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 tool is simple (2 params, full schema coverage, annotations present, no output schema), so the bar is low, but with no return-value description and no routing versus get_rates or convert, the agent is left to guess at both. The single sentence does not cover what an agent needs to select and interpret this call.

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?

Schema description coverage is 100%, so both parameters are fully documented in structured form. The description's "any base currency" reinforces that base is a free-form ISO code, but adds no syntax or meaning beyond that, and the date parameter is untouched. Baseline 3 applies when the schema carries the explanation.

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 same snapshot re-expressed against any base currency" conveys the resource (a rate snapshot) and the key operation (re-basing), but it is a noun phrase with no explicit verb and never says plainly that it returns exchange rates. The phrase "the same snapshot" alludes to get_rates without naming it, so an agent must infer the relationship rather than read it.

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?

There is no when-to-use guidance: no mention of when this is preferable to get_rates or convert, and no stated prerequisites (e.g., that the base must be supported). "Any base currency" hints at cross-rate use but leaves the choice among siblings entirely to inference.

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