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

The annotations already declare readOnlyHint=true, so the description need not restate read-only behavior. It adds context about the time-series shape and the breakdown by embed type, but does not disclose other behavioral traits like aggregation interval, response size, or how missing embed values are handled.

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 two sentences with no filler; the core output and breakdown are stated first, followed by a direct usage rationale. Every sentence earns its place.

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 one optional, fully documented parameter, a read-only annotation, and an output schema, the description is nearly complete for correct invocation. It could be stronger by explicitly contrasting with get_active_sessions_over_time, but the embed-breakdown language already routes an agent reasonably well.

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?

The only parameter, time_filter, is fully and clearly documented in the schema with presets, a custom-range pattern, defaults, and inclusivity semantics. With 100% schema description coverage, the tool description has no obligation to repeat parameter details, and it adds no extra meaning beyond what the schema 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 states a specific resource and dimension: a time series of active sessions broken down by embed type, with the enum of embed types explicitly listed. It differentiates from sibling get_active_sessions_over_time by emphasizing the breakdown, though it does not explicitly name that sibling or state what the tool is not.

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?

'Use this to understand which interfaces are driving usage' gives clear and relevant context for when the tool is the right choice. It does not mention alternatives or exclusion cases, such as when total active sessions without a breakdown would be more appropriate.

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