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

The annotations already mark this as read-only and not open-world, so the description doesn't need to repeat that. It adds valuable context beyond the annotations by revealing the calculation formula, data source (ECB reference rates), output components, and daily update cadence. No behavioral surprises are hidden.

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 packed into two efficient sentences: the first delivers the core purpose and methodology, the second covers use cases and update frequency. Every clause earns its place, and it remains highly readable despite the technical density.

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?

With no output schema, the description compensates well by enumerating expected return components (score, basket contributions, history, methodology_version). It also explains data freshness ('Updates: daily'). However, it doesn't explicitly state the default behavior or how the optional 'days' parameter changes the response, though the schema covers 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?

There is only one optional parameter, 'days', and its schema description fully covers its purpose, range, and tier requirement. The tool description itself adds no extra parameter semantics, but since schema coverage is 100%, the baseline of 3 is appropriate.

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 opens with 'Returns a 0-100 US dollar strength score', a specific verb and resource, and then enriches with the exact methodology (geometric index, DXY basket, 60/40 weighting). This clearly distinguishes it from the many sibling tools and leaves no ambiguity about what it computes.

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?

It explicitly lists when to call: 'when the user asks about dollar strength, USD strengthening or weakening, or DXY-style direction, or when timing FX hedges...'. This provides clear usage context, but it does not mention any when-not scenarios or direct alternative sibling tools, so it stops short of a 5.

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