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

Annotations already declare the tool as read-only, idempotent, and non-destructive. The description adds valuable behavioral context: data source (ECB), date availability range (1999-01-04 onward), and format example. Output schema handles return values, so no additional explanation needed.

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 with no redundancy. The first sentence states the core purpose immediately, followed by specific constraints and an example. Every sentence adds value.

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 (3 parameters, output schema present, rich annotations), the description covers all necessary contextual details: data source, date range, and usage example. It is fully sufficient for correct invocation and selection.

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 descriptions for base, date, and symbols. The description provides an example that mirrors the schema but does not add new meaning beyond what the schema already conveys. No parameter semantics are enhanced.

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 retrieves exchange rates for a specific historical date, using a specific verb ('Get') and resource ('exchange rates'). It distinguishes from siblings like 'get_latest' and 'get_timeseries' by focusing on a single historical date, and provides an example to reinforce this.

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 usage for historical single-point queries via phrasing 'specific historical date' and the example. While it doesn't explicitly exclude alternatives, the context is clear and the sibling list includes related temporal tools, allowing inference. No exclusions are needed.

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