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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior, so the description carries a lighter burden. It adds useful context about the returned content (definitions, data sources, caveats), but it does not disclose potential limitations such as missing metadata for some indicators or response formatting.

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 two sentences with no filler. The first sentence front-loads the return contents in a scannable dash clause; the second adds usage timing. Every word earns its place.

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?

For a single-parameter, read-only metadata lookup, the description fully covers what the tool returns and when to use it. The absence of an output schema is mitigated by the explicit enumeration of metadata contents.

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%: the single required 'measure' parameter is documented with a type and example ('HFA_1'). The description adds no further parameter-level detail, so it meets the baseline but does not exceed it.

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 uses a specific verb ('Get') and names the exact resource: definition, data source, and footnotes for a WHO Europe health indicator. It further clarifies the content (calculation method, supplying organisation, country-specific caveats), which clearly distinguishes it from value-returning siblings like who_euro_measure_data.

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 final sentence gives explicit usage context: 'Use before comparing European health indicator values across countries or years.' This tells the agent when the tool is relevant, though it does not name alternative tools or explicitly state when not to use it.

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