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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the tool is known to be safe. The description adds no additional behavioral context beyond its purpose, such as output format, data sources, date handling, or edge cases. It merely restates what the tool does, offering no value beyond 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?

The description is a single, front-loaded sentence beginning with the verb 'Build.' It efficiently conveys the chart type, comparison elements, and purpose without extraneous words or repetition.

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 fully documented parameter schema and read-only annotations, the description provides sufficient context for a chart-building tool. However, it could elaborate on what constitutes a 'rate differential setup' or the output format, leaving a minor gap in completeness.

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 all four parameters, including supported currency codes and date format examples. The description adds no new semantic meaning beyond the schema; it only mentions base and quote in passing, which is already fully documented.

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 the tool builds a two-series chart comparing base and quote policy-rate history, which is a specific verb and resource. It distinguishes itself from sibling visual artifact tools by focusing on policy-rate differentials for FX pairs, making its purpose unambiguous.

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 implies a use case—visualizing policy-rate differentials—but does not explicitly state when to use this tool versus alternatives like forex_visual_artifact or rate_differentials. No exclusions or alternative tool mentions are provided, leaving usage guidance implied rather than explicit.

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