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

Goes well beyond the annotations by disclosing the exact side effects: half of not-yet-contacted leads are moved out of the original into a new DRAFTED campaign, the flow is copied, and the original is renamed to '<title> [A]' leaving it with half its audience. It also quotes the failure mode and error string. Although the audience loss on the original sits in some tension with destructiveHint=false, leads are moved rather than deleted and the outcome is fully disclosed, so this is not a contradiction.

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?

Front-loads the decisive fact (splits, not copies) in the first sentence, then layers side effects, precondition, and the alternative in descending importance. Dense with no filler despite its length.

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?

One parameter, no output schema, so the description only needs to cover selection logic and consequences. It covers both thoroughly, including the exact error message and the backend's own suggested fallback.

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% and the single `campaignId` parameter is already documented as coming from `campaign_list` or `campaign_create`. The description adds no syntax, format, or constraint detail beyond what the schema provides, so the 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?

States a specific verb and resource (split a campaign into an A/B pair) and immediately distinguishes it from the confusingly similar `campaign_duplicate` by insisting 'This SPLITS, it does not copy.' An agent can select correctly without opening the 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?

Gives explicit routing rules in both directions: use `campaign_duplicate` when the audience should be left alone, use this when the point is to compare two versions on one audience. It also states the precondition (>10 contacts still waiting) and points to `analytics_campaign` for the follow-up comparison.

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