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

Adds behavioral context beyond annotations: specifies returned fields (validFor, rate, volume) and data freshness (verified live). No contradictions with annotations (readOnlyHint, idempotentHint). Weekend/holiday behavior is in schema, not description, but description still adds value.

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?

Three concise sentences: defines the acronym, lists return fields, and provides usage tip. Front-loaded with the most important information; every sentence earns its place without redundancy.

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?

Adequately covers tool purpose, input usage, and key outputs despite lacking an output schema. Could be slightly improved by noting the format of the returned rate or volume, but sufficient for a simple one-parameter lookup tool.

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 coverage is 100% with detailed parameter description (date format, omission for latest, weekend/holiday handling). Description merely restates 'Omit date for the latest', adding no new semantic value beyond the schema.

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?

Clearly states the tool returns CZEONIA (Czech Overnight Index Average) for a given day with specific outputs (validFor, rate, volume). Distinguishes from sibling tools by naming the exact index and contrasting with other CNB tools like exchange rates or PRIBOR.

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?

Indicates when to omit the date parameter (for latest). Does not explicitly state when to use this tool versus alternatives like cnb_pribor or cnb_exchange_rates, leaving the agent to infer based on the specific rate name.

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