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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is fully covered. The description adds useful content about what the payload contains (running tests, per-version results, verdicts with confidence), but adds nothing about scope, filtering, or freshness — and the output schema likely carries the return shape already.

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 sentence, front-loaded with the resource and then the two categories of returned data. The parenthetical list is efficient; the phrasing is slightly awkward but 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 no parameters, annotations covering safety, and an output schema present, the description only needs to convey scope and usage, which it half does: it explains what comes back but not which tests (all campaigns? one account?) or when this is the right tool. Adequate but leaves a real gap.

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 tool takes zero parameters, so there is no parameter semantics for the description to explain. Baseline 4 applies; nothing is missing or misleading on this dimension.

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 identifies the resource precisely — split tests — and enumerates returned content (per-version numbers, verdicts, winner, rate, confidence). But it is a noun phrase with no verb, so the agent must infer whether this lists, retrieves, or summarizes tests, and it makes no attempt to distinguish itself from siblings like ad_performance or get_ad_campaign.

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?

There is no statement of when to call this versus ad_performance, get_ad_campaign, or ads_overview, and no prerequisites or exclusions. The agent is left to guess the usage context from the resource name alone.

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