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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds that results are global, country-level rows scoped to a single index family, which is useful context. It gives no detail on pagination, result size, or freshness — a modest but not rich addition.

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?

Two sentences, zero waste. The core purpose is front-loaded and the sibling-routing is packed into a single follow-up sentence.

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?

With an output schema present, return values need not be described, and read-only annotations cover safety. For a single required parameter tool, the description is essentially complete; only minor behavioral detail is absent.

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% and the `index` parameter already enumerates the valid families in the schema. The description only repeats 'one `index` family' without adding format, defaults, or selection guidance. Baseline 3 is appropriate when the schema does the heavy lifting.

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?

States a concrete verb+resource: 'Fetch Numbeo's global country-ranking rows for one `index` family'. It names sibling tools, helping an agent separate it from numbeo_indices_rankings and numbeo_indices_country. The remaining ambiguity is what 'by_country' adds over the 'general' ranking, but overall the purpose is clear.

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?

Explicitly routes to three alternatives: numbeo_indices_rankings for a general ranking, numbeo_indices_city for city comparisons, numbeo_indices_country for one country's values. This tells the agent when to pick a sibling instead, though it doesn't state a when-not for this tool itself beyond the implicit inverse.

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