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

The annotations already declare readOnlyHint=true and openWorldHint=false, so the agent knows this is a safe read-only query. The description adds that this is a time series broken down by embed type, but does not add deeper behavioral context beyond what the annotations and input schema already convey.

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 wasted words. It front-loads the core behavior and then immediately provides a practical use case, 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?

For a read-only analytics tool with one optional, fully documented parameter and an output schema, the description is complete enough. It states what the tool returns, what the grouping dimension is, and when to use it; nothing essential is missing.

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 input schema has 100% description coverage for the single time_filter parameter, including accepted presets, custom date range format, and the default value. The tool description itself does not mention time_filter, so it adds no parameter semantics, but the schema already carries the full burden.

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 a specific verb and resource: it gets active sessions broken down by embed type, listing the embed types explicitly. It is distinct from get_active_sessions_over_time through the 'by embed type' grouping, though it does not name the sibling to make the distinction explicit.

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 gives a clear use case: 'Use this to understand which interfaces are driving usage.' It provides context for when to select this tool but does not mention exclusions or alternatives, such as when get_active_sessions_over_time 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.