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

Annotations already indicate destructiveHint=true and readOnlyHint=false, so the mutation nature is disclosed. The description adds useful context: it is date-scoped and limited to multicurrency companies. However, it does not explain what happens if a rate already exists for that date (overwrite), or any side effects. Given the annotations carry the safety profile, the description adds moderate behavioral context but not rich detail.

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 a single, concise sentence that front-loads the core action and includes the critical constraint. Every word earns its place with no filler. It is appropriately brief for a tool with a well-covered schema.

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 has a nested required parameter and no output schema. The schema provides the structure, and the description gives the core intent. However, it lacks any information about return values, error conditions, or behavior on existing rates. For a mutation tool with no output schema, an agent might need to know what to expect after invocation. Given the simplicity, a 3 is fair, but it could improve by mentioning overwrite behavior or confirmation of success.

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% for both parameters. The entity property has an explicit description showing the exact structure and noting that exchange rates have no Id or SyncToken. The description itself adds no additional parameter meaning beyond the schema. Since the schema is thorough, a baseline of 3 is appropriate; the description does not need to supplement.

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 clearly states a specific action ('Set the exchange rate'), the resource (exchange rate), and the exact scope (for a currency on a given date). It also includes a critical constraint (multicurrency companies only), which distinguishes it from currency-related tools like update_company_currency. An agent can immediately understand what this tool does and when it applies.

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 offers no guidance on when to use this tool versus alternatives such as get_exchange_rate or search_exchange_rates. There is no mention of prerequisites (e.g., checking existence) or exclusions. It only states a constraint (multicurrency companies only) but does not clarify that this tool is for setting/updating rather than reading. An agent would need to infer usage from the name and description alone.

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