customer_insights_regions

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

Annotations declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, destructiveHint=false. The description adds behavioral detail about the response structure, region values, and that usersPercent sums to ~100. It also notes that productId/hosting are ignored, which is beyond the annotations.

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 concise and front-loaded with the main purpose. Each sentence adds value (response shape, region list, filtering note, spec link). The link to external spec is slightly extraneous but does not detract significantly.

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?

For a simple read tool with no output schema, the description adequately explains the return structure, filtering, and region values. It covers key aspects like usersPercent summing to ~100 and the benchmark. Minor gaps remain, such as not clarifying the optionality of the benchmark.

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 100% with descriptions for both parameters. The description adds context about filtering behavior and response structure, but does not significantly go beyond the schema's parameter descriptions. 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?

The description clearly states the tool's purpose: 'Geographic-region distribution of your customers' users, per month.' It specifies the verb (returns distributions) and the resource (customer users' geographic regions). It distinguishes from sibling tools like customer_insights_active_users by focusing on regions.

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 usage context by stating that only startDate/endDate filters work and that productId/hosting are ignored. However, it does not explicitly tell when to use this tool versus alternatives or when not to use it.

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