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

Annotations already mark this as a mutating, non-idempotent creation with openWorldHint. The description adds ownership semantics, the rule that ruleset forms the first leg, and that other fields pass through to play for validation—useful behavioral context beyond the annotations.

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?

The description is three dense sentences with no filler, front-loading the core purpose and required parameter before the leg/validation context. Every sentence contributes essential 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?

For a create operation with an output schema and annotations, the description covers ownership, required input, the ruleset-specific leg model, and validation. The only minor gap is not detailing potential validation errors or how settings should be structured, but these are not essential for invoking the tool.

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 input schema exposes no properties, so the description carries full responsibility for parameter information. It identifies name as required, explains the ruleset leg behavior, and lists summary, description, and settings as pass-through fields—substantial semantic value.

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 uses a specific verb+resource ('Create a new campaign') and adds that it is owned by the calling user. This clearly differentiates it from sibling create tools like play_create_session or play_create_page, and the campaign concept is unambiguous.

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?

It states the required name, explains the special ruleset leg behavior, and explicitly points to play_add_campaign_leg for adding more legs. It does not explicitly enumerate when not to use it (e.g., updating an existing campaign via play_update_campaign), so it misses a small exclusion.

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