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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely useful behavioral context beyond that: credential-free public Numbeo data and the fact that one scope is continuously updated while the other is a frozen historical snapshot. It stops short of describing pagination or ranking granularity, so not a 5.

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?

Front-loaded with the core purpose, followed by data-source context and the sibling pointer. The parenthetical list of six indices is slightly dense but informative rather than wasteful. Mostly efficient, with only minor redundancy in restating the scope enum.

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 need no explanation. The description covers what is returned, the two data modes, the data source's credential-free nature, and the sibling to use for country rankings. Nothing an agent needs to call this correctly is missing.

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 the schema already documents both scope and period, including the 'required when scope=historical' rule and an example snapshot id. The description restates the scope options but adds no syntax or semantics beyond what the schema provides. Baseline 3 is appropriate.

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 verb (Returns) and resource (global cost-of-living city ranking), enumerates the indices returned, and explicitly distinguishes itself from numbeo_cost_of_living_rankings_by_country. An agent can tell it apart from the country-ranking sibling without opening either schema.

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?

Names the alternative tool (numbeo_cost_of_living_rankings_by_country) and the condition that selects it (country vs city ranking), which is strong routing guidance. It does not, however, address the other close siblings numbeo_indices_rankings or numbeo_cost_of_living_city, so the guidance is clear but not exhaustive.

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