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

Annotations already declare the operation as read-only, idempotent, and non-destructive, so the description does not need to restate that. It adds useful context about the returned data, but it does not disclose behavior for missing regions, invalid country values, or whether the country parameter must be a slug or display name.

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 sentences, each earning its place: the first defines the resource and its contents, the second explains downstream usage, and the third clarifies slug formatting. It is front-loaded and free of filler.

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 no output schema, the description carries the burden of explaining return values, and it does describe names, slugs, postal codes, and area codes. However, it omits guidance on the 'country' parameter, possible empty results, and slug source or validation, leaving an agent uncertain in non-standard cases.

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 only 50%: 'region' has a description but 'country' does not. The description compensates well for 'region' with slug format and examples ('texas', 'ile-de-france', 'alger'), but it leaves the 'country' parameter entirely unexplained, so the agent still lacks complete parameter semantics.

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 clearly states what the tool returns: a region with its cities/départements/delegations, including names, slugs, postal codes, and US area codes. This is specific and goes beyond the tool name, though it does not explicitly differentiate itself from sibling tools like area_code_lookup.

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 description gives useful guidance on how to use the returned slugs ('Use the slugs it returns to call get_group or get_place'), which implies a follow-up workflow. However, it does not state when to choose this tool over alternatives such as search_places, list_countries, or lookup_postal_code.

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