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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is known. The description adds useful behavioral context by documenting the optional API key via headers or query parameter and its effect of selecting Pro automatically when valid, which goes beyond the structured 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 two compact sentences with no filler. The first sentence front-loads the exact scope, and the second sentence adds the API-key/Pro behavior. Every word 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 simple two-parameter enum-driven tool with an output schema and safety annotations, the description plus schema covers what an agent needs to select and invoke it. The only minor gap is that it doesn't clarify what the returned forecast structure contains, but the presence of an output schema reduces the need for that.

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 0%, so the description must compensate. It does help by translating enum-like indicator values into readable series (e.g., USD/EUR, dollar index, euro FX vol), but it doesn't explicitly document the timeframe parameter or the exact mapping between enum values and series beyond the names. The enum values themselves are partially self-explanatory, keeping this minimally adequate.

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 identifies the resource as 'USD FX and volatility forecasts' and enumerates the specific series covered: USD/EUR, USD/AUD, USD/CNY, dollar index, and euro FX vol. This is specific enough to distinguish it from sibling forecast_commodities, forecast_equities, and similar tools.

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 conveys that this tool is for currency and FX-volatility forecasts by naming actual currency pairs and the dollar index. It doesn't explicitly state 'use this instead of forecast_commodities', but the asset-class focus gives clear context, and no exclusions are needed given the sibling names.

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