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. The description adds real behavioral value by defining the hook rate and completion rate formulas, which an agent cannot infer from structured fields. However, it says nothing about ranking window, how ties or low-volume creatives are handled, or whether the 'best/worst' selection is fixed-size.

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 with the ranking action first, then the metrics, then the formula clarifications in parentheses. No filler, no restatement of the name or 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 read-only analytics tool with a fully documented 7-parameter schema and no output schema, the description covers what is measured and how two derived metrics are computed, which is enough to call it correctly. The minor gap is that the return shape of the ranked list (sections, row counts) is only hinted at through the 'detail' parameter rather than stated.

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 100%, so every parameter (detail, folder, account, dates, language) is already documented in the schema, and the description adds no parameter guidance of its own. Baseline 3 applies when the schema does the heavy lifting, and the metric definitions here relate to output rather than inputs.

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 gives a specific verb and resource ('Rank ads by efficiency: best and worst creatives by cost per result and CTR') and explicitly defines the derived metrics (hook rate = 2s views / impressions, completion rate). This distinguishes it from siblings like tiktok_ads, tiktok_breakdown, and meta_creative_insights without opening a schema.

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 by the ranking framing — use this when the user wants to know which creatives are efficient or inefficient — but there is no explicit when-to-use or when-not guidance, and no mention of how it differs from tiktok_ads or tiktok_breakdown. The only routing guidance lives in the schema's 'detail' parameter description, not in the description itself.

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