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

Annotations already cover safety (readOnlyHint=false, destructiveHint=true, idempotentHint=true), so the bar is lower. The description still adds real value by disclosing the downstream effect (campaigns skip the mailbox) and the state precondition, though it doesn't say whether the pause is reversible or how it interacts with running campaigns.

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, zero filler, with the effect front-loaded before the precondition. Every clause earns its place.

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 mutation with annotations covering the safety profile and no output schema, the description supplies the essential effect and precondition. It is nearly complete, missing only reversibility/resume guidance.

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 (`id`) with 100% schema description coverage, so the schema already carries the semantics. The description adds nothing about the id beyond what the schema states, making the baseline 3 appropriate.

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 ('Stop') and resource ('mailbox') plus the operational effect ('campaigns skip it'). It does not explicitly contrast with the sibling resume_mailbox, so it falls just short of 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?

Gives a clear precondition — only an `active` mailbox can be paused — which tells the agent when the call is valid. It stops short of naming the alternative (resume_mailbox) or stating when pausing is preferred over other mailbox operations.

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