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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is fully covered. The description's one addition, the 'stable snapshot' consistency guarantee, is genuinely useful behavioral context, but pagination, result limits, and large-range behavior are left to the schema.

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?

Two tightly written sentences, front-loaded with purpose before the alternative-tool guidance. No filler or redundant restatement of the name.

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 12-parameter tool with nested filter objects, enums, and grouping semantics, the description is thin on how group_by and metrics interact and on pagination limits. The output schema and annotations cover return values and safety, but the behavioral/parameter guidance an agent needs for complex calls is only partially present.

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 67%, so roughly a third of parameters (order_by, cohort_ids, include_unidentified, analysis_status, intent_family) are undocumented in either place. The description adds no parameter-level meaning beyond the vague 'grouped totals and rates,' so it does not compensate for the gap.

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 and resource ('Aggregate sessions inside Flowlines') and explicitly contrasts itself with the sibling list_sessions, so an agent can distinguish it without opening either schema. The 'stable snapshot' framing sharpens what the aggregation operates on.

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?

Gives a clear use condition ('grouped totals and rates') and names the alternative to avoid ('downloading sessions through list_sessions'), which is strong routing guidance. It stops short of explicit when-not edge cases (e.g., single-session lookups should go to get_session) or prerequisites.

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