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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful context beyond that: the result is a deterministic sample, and it carries end-user PII that should be quoted minimally and masked. It doesn't mention auth or rate limits, but for a read-only tool with full annotation coverage this is a solid addition.

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, core purpose front-loaded, an alternative-routing clause, then the PII caveat. Every sentence earns its place with no 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?

An output schema exists, so return values needn't be described, and annotations cover the safety profile. The remaining shortfall is the undocumented half of the parameters, a gap the description could have partially closed for such a wide tool.

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 44% (range, search, cohort_id, minimum_sessions, and include_unidentified are undocumented). The description says nothing about any of the nine parameters, so it fails to compensate for the coverage gap; 'totals and deterministic sample' only loosely gestures at point_limit.

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 (Return) and two concrete resources: exact user-population totals and a deterministic sample of graph-ready user points. It also explicitly names the sibling it differs from (list_users), so an agent can distinguish it from get_map, get_user_activity, and search 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?

Names the alternative (paging list_users) and the precise condition that selects this tool instead ('when the user asks for a population graph or distribution'). Nothing about when to reach for it is left to inference.

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