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

Annotations already establish readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds useful scope context ('for the account or one campaign') and discloses the metric set, but says nothing about result limits, pagination, empty-data behavior, or how rows are ordered.

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?

A single front-loaded sentence that puts the segmentation axes before the metric list, with zero filler. The enumerated lists are dense but readable and every clause carries information.

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 8 parameters and no output schema, the description usefully compensates by naming the metrics returned and the available dimensions. The remaining gaps (aggregation granularity, result limits) are modest for a read-only reporting tool whose annotations and schema cover the rest.

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 75%, so the schema already documents most parameters including the dimension enum. The description adds a little meaning by expanding OS to 'iOS/Android' and clarifying that campaign scope is optional versus account-level. It adds nothing for date_range, start_date/end_date, folder, or language.

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 names a specific verb ('break ... down') and resource ('Snapchat performance'), and enumerates the exact segmentation axes (age, gender, OS, country, region) and metrics returned. It implicitly separates itself from snapchat_performance by being the segmented view, though it never names that sibling explicitly.

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?

Usage is implied: reach for this when you need performance split by demographic/geo/OS rather than an aggregate. There is no explicit 'use X instead when...' routing against snapchat_performance or snapchat_wasted_spend, and no prerequisites (e.g., account must be enabled) are stated.

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