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

Annotations already declare readOnlyHint and openWorldHint, and the description adds context beyond them: 'Credential-free public Numbeo data' conveys the auth posture and data provenance, and 'grouped by category' hints at output structure. It stops short of describing rate limits or data freshness.

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 short sentences, front-loaded with purpose and categories, then provenance, then the sibling routing hint. Nothing is redundant except a minor restatement of the slug format.

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 not be explained, and annotations cover the safety profile. The description still supplies provenance, a category overview, and sibling routing, so nothing an agent needs to call it 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% for the single required slug parameter, so the schema already carries the format. The description's 'slug: Numbeo city slug, e.g. Los-Angeles' merely restates the schema rather than adding syntax or edge-case detail, matching the baseline-3 case.

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), resource (itemized cost-of-living prices), and scope (for one city), and enumerates the categories covered. An agent can distinguish it from numbeo_cost_of_living_country and the numbeo_indices_city siblings without opening a 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?

Explicitly names an alternative ('Use numbeo_cost_of_living_country to get a Numbeo country's cost-of-living prices') with the condition that selects it. It does not address the indices siblings a caller might also consider, but the country/city routing is clear.

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