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

Annotations already indicate readOnlyHint, and the description adds useful behavioral context: the 0-100 scale, fixed 6-currency weights, live spot rates, hourly updates, and history to 1999. It also lists returned fields. This goes beyond the annotation without contradiction.

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 dense and front-loaded with the core purpose, followed by usage triggers and update frequency. It contains no unnecessary fluff, though the long run-on sentence could be slightly better structured for readability.

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 the tool's simplicity (zero required parameters) and lack of output schema, the description covers the essential aspects: the score's meaning, formula basis, update cadence, returned fields, and usage scenarios. It is sufficiently complete for an agent to select and invoke the tool correctly, though a bit more detail on the output format would help.

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?

The schema fully describes the single optional parameter 'days' with range and tier requirement (100% coverage). The tool description itself adds no additional parameter semantics beyond what the schema already provides, so the baseline score 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 clearly states this tool returns a US dollar broad-strength score on a 0-100 scale, explicitly naming it as an ICE DXY proxy with specific fields (dxy_proxy_score, dxy_proxy, eurusd) and a defined formula. It distinguishes itself from possible sibling tools by these specific attributes and use-case triggers.

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 provides explicit when-to-use guidance, listing many concrete triggers such as questions about dollar strength, DXY, EUR/USD, exchange rates, FX basket moves, and hedging scenarios. However, it does not mention when NOT to use this tool or suggest alternatives, so it stops short of a perfect score.

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