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

Annotations already disclose that this is a non-read-only, non-destructive, non-idempotent operation. The description adds the useful 'running' state constraint, but it does not explain what happens when pausing an already-paused campaign, whether sends halt immediately, or what the response returns. With annotations covering the safety profile, a 3 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 a single short sentence with no wasted words, and the action is front-loaded. It is appropriately sized for a simple toggle operation, though it could have used the space for one routing or state caveat.

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 simple one-parameter mutation with annotations and full schema coverage, the description is minimally complete. It still omits the likely non-idempotent behavior (pausing twice may error) and the relationship to start_campaign, which an agent would benefit from knowing.

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?

There is only one parameter, and schema coverage is 100%; the schema itself documents campaign_id as coming from list_campaigns. The description adds no additional meaning about the identifier format or sourcing beyond what the schema already 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?

The description states a specific verb and resource: 'Pause a running campaign.' An agent can immediately tell this changes campaign state. However, it does not differentiate from sibling tools like start_campaign, resume_mailbox, or pause_mailbox, so it stops short of the sibling-routing clarity that earns a 5.

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 word 'running' implies a state precondition (the campaign must currently be active), which gives some usage context. But there is no explicit guidance on when to choose this over start_campaign or update_campaign, and no mention of what to do if the campaign is already paused.

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