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

Beyond the annotations (destructiveHint=true, idempotentHint=true, readOnlyHint=false), the description discloses atomicity ('Upserts and removals in one call are atomic; an ambiguous request changes nothing'), that no rate is ever fetched or refreshed, that stored amounts are never rewritten, that rates affect only fully-covered display aggregates, and that the call is admin-only and returns the default currency plus the full rate table. This is unusually rich behavioral context that does not contradict the 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?

Purpose and scope are correctly front-loaded, but the core rate-direction semantics are stated three times: in the intro paragraph, again in the 'When to use' block, and again in the example. Roughly a third of the text is redundant restatement rather than new information.

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 an output schema exists (so return values need not be explained, though they are), full schema coverage, and annotations covering safety and idempotency, nothing an agent needs to invoke this correctly is missing: direction of the rate, atomicity, admin requirement, and currency constraints are all present.

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 the baseline is 3, but the description adds genuine meaning with a concrete worked example ('with DKK as the default, {currency:"EUR",rate:7.46} means 1 EUR = 7.46 DKK'), clarifying the direction of the rate that the schema's terse phrasing only implies.

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 opening sentence names a specific verb pair and resource: 'Set or remove the workspace's customer-authored manual exchange rates.' No sibling tool touches exchange rates, so the agent can immediately distinguish this from the CRUD/meeting/report siblings in the list.

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?

An explicit 'When to use' block scopes the tool to admins who want aggregate money reads converted into the workspace default currency with customer-owned rates. It states no rate feed or automatic update is involved, though it does not spell out a when-not-to-use condition or name an alternative tool (there is no obvious sibling alternative).

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