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

Annotations already declare non-read-only, idempotent, non-destructive, so the safety profile is covered. The description still adds real value beyond them: the banner is pulled from signatures (a downstream side effect outside this resource) and the failure mode CAMPAIGN_NOT_ACTIVE is named. It doesn't say what happens when pausing an already-paused campaign.

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?

Two tight sentences: the action and its effect first, then the refusal condition. No filler and nothing that could be trimmed without losing 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 single-parameter state-change tool with annotations and no output schema, the description covers action, side effect, precondition and error. The only gap is the already-paused case and whether any return payload is produced.

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?

Only one parameter and schema coverage is 100%, with the schema already stating it comes from list_campaigns. The description adds nothing about the id beyond what the schema provides, so 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 ('Pause') and resource ('campaign') plus the downstream effect on banners in signatures. The RUNNING-only framing implicitly separates it from resume_campaign and delete_campaign, but no sibling is named explicitly.

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 an explicit precondition (must be RUNNING) and an explicit exclusion (scheduled campaigns have nothing to pause) with the resulting error code. It does not name resume_campaign or delete_campaign as alternatives for other desired outcomes.

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