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

Annotations already declare readOnly, idempotent, non-destructive, and not open world. The description adds a behavioral constraint (date range of at most 60 days) that is not in annotations, but the statement 'This does not change assets or delivery' is redundant. No auth, rate limit, or output format details are provided.

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 sentences with zero waste. The core functionality is front-loaded, and the secondary clarification is brief and non-redundant in structure.

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?

Given an output schema and annotations covering safety, the description provides the essential purpose and a key constraint (60-day limit). It does not explain breakdown array limits or filter behavior, but those are in the schema. The lack of sibling differentiation is a minor gap for an agent choosing among similar analytics tools.

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 description coverage is 100%, so the schema already documents all parameters. The description repeats schema-level details like 'grouped by a breakdown field' and 'date range of at most 60 days' without adding syntax or meaning beyond what is in the schema. Baseline 3 applies.

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 verb (Read), resource (viewer metrics), and scope (one workspace, grouped by a breakdown field, date range of at most 60 days). It clearly distinguishes itself from generic asset management tools, but it does not differentiate from closely related siblings like analytics_breakdown_data or insights_aggregated_data.

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?

No explicit guidance on when to use this tool versus alternatives. It provides a constraint (max 60 days) and notes it doesn't change assets, but does not say when to choose this over other analytics tools or what prerequisites exist.

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