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

Annotations are all false (readOnlyHint=false, etc.), so the description carries the burden of behavioral disclosure. It adds useful context: the call requires 'contribute' permission and is rate-limited per caller and per campaign. However, it does not mention that the invite creates a pending state that the invitee must accept, nor does it describe any side effects beyond sending the invite. It does not contradict the annotations, so a mid-range score is appropriate.

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 two sentences with zero fluff. The first sentence states the primary action, and the second provides two critical constraints (permission and rate limiting). Every word contributes to the agent's decision-making. It is perfectly front-loaded and appropriate in 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?

The description covers the core action and constraints but omits some operational context that an agent might need, such as whether the invitee must be a friend or what happens if the user is already in the campaign. The existence of an output schema reduces the need to explain return values, but the description could still benefit from noting that the invite is pending until accepted. Overall, it's adequate but not exhaustive.

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 description coverage is 100%, so all three parameters have descriptions in the schema itself. The tool description adds no additional parameter meaning; it merely restates the permission requirement and rate limit. Since the schema already documents the role enum and the userId/campaignId semantics, the description provides no extra value for parameter understanding, warranting the baseline score of 3.

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 clearly states the action: 'Send a campaign invite to another user.' It identifies the resource (campaign invite) and the target (another user). It does not explicitly differentiate from sibling tools like play_respond_to_campaign_invite, but those are distinct enough in name and action. The permission requirement adds specificity, but the description could be stronger by naming the closest sibling alternative.

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 description does not mention when to use this tool versus alternatives. It only states a prerequisite (caller must have 'contribute') and a rate-limit caveat. There is no guidance on when not to use it, such as 'For invite-by-email, use play_find_friend first' (though that hint exists in the schema). The absence of any sibling comparison or exclusions leaves the agent without explicit routing context.

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