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 nothing behavioral beyond restating the schema's 'current or historical' option — no note on what the ranking returns, how it's ordered, or any update cadence.

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?

A single short sentence, front-loaded with the resource and scope. It is efficient and wastes no words, though the parenthetical merely echoes the schema's scope parameter.

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?

An output schema exists, so return values needn't be explained, and the parameter schema is complete. The remaining gap is routing: with several closely-named rankings siblings, the definition should clarify scope/order, leaving it only minimally adequate.

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%, so both `scope` and `period` (including the snapshot-id example 2026-mid) are already fully documented in the schema. The description adds no format or usage detail beyond that, so the baseline of 3 applies.

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 specific resource (Numbeo cost-of-living city ranking) and scope ('Global'), which implicitly distinguishes it from the country-scoped sibling numbeo_cost_of_living_rankings_by_country. The distinction is only implied by the word 'Global', however, and is never made explicit against the several rankings/indices siblings.

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?

There is no when-to-use guidance at all: nothing tells the agent how to choose between this, numbeo_cost_of_living_city, numbeo_cost_of_living_rankings_by_country, or the indices_rankings variants. The current-vs-historical choice is only resolved by the schema, not the description.

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