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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is covered. Beyond that the description says nothing behavioural — not what the output card looks like, not that summary detail truncates rows, not any scoping or rate constraints. It adds essentially no context over the structured fields.

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 short sentences, front-loaded with the resource and the dimensions, with the optional campaign scope last. No filler, no repetition of the title.

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 9-parameter reporting tool with no output schema, the description explains the core axis (dimension) and the optional campaign scope, which is the minimum an agent needs to pick and call it. It leaves open what metrics and row structure come back and how the detail/date_range controls interact, so it is adequate rather than complete.

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 78%, so the baseline is 3, and the description does add real meaning in two places: it expands 'platform' to Android/iOS and spells out the six allowed dimensions, and 'Optionally for one campaign' documents the campaign parameter's role as an optional filter, which the bare schema leaves undefined. It says nothing about detail, date_range, folder, account or language, but those are described in the schema.

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 verb 'Break performance down by' plus the enumerated breakdown dimensions (age, gender, country, platform, network, language) states precisely what the tool returns, and the dimension list mirrors the enum so an agent can match intent quickly. It does not, however, name or contrast itself with near-siblings like tiktok_performance or tiktok_report_query, so the agent must infer the boundary.

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 only usage-shaped statement is 'Optionally for one campaign', which is a scoping detail rather than a when-to-use rule. There is no guidance on when a breakdown is preferred over tiktok_performance or tiktok_report_query, and no exclusions or prerequisites (e.g. account must be enabled, which dimension fits which question).

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