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

The annotation readOnlyHint=true already indicates a safe read operation, lowering the burden. The description adds that breakdown is by geographic levels, but it doesn't mention return format, pagination, or the need for a site parameter. These are partly covered by schema, so the description adds minimal behavioral context beyond the annotation.

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?

The description is a single concise sentence of eight words, front-loading the core purpose. There is zero redundancy or filler, making it easy for an agent to parse quickly.

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?

Given the simple read-only nature and a fairly informative schema, the description is adequate but minimal. It lacks explicit usage comparison with siblings and does not describe the expected output structure, especially since there is no output schema. The description covers the essential purpose but leaves some gap for decision-making.

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 75% (site, limit, range have descriptions), so the baseline is 3. The description only repeats the enum values for dimension without adding extra meaning. It doesn't explain parameter dependencies or defaults beyond what the schema already provides.

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 the tool's function: 'Visitor breakdown by geography' and lists the available dimensions (country, region, or city). This specific verb+resource+scope distinguishes it from sibling tools like get_traffic_sources or get_pages, making the purpose unambiguous.

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 provides no guidance on when to use this tool versus alternatives. It doesn't mention whether to prefer this over get_traffic_sources or get_audience, nor does it state any exclusions. The only implicit hint is the name and dimension list, which is insufficient for a tool with many siblings.

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