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

The description adds meaningful context beyond the annotations by explaining the effect, campaigns reach them again, and the consent prerequisite. The annotations already cover the write/destructive/non-idempotent profile, so this is a strong but not fully exhaustive disclosure.

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 sentences, front-loaded with the WRITE marker and the core state change. Every sentence carries operational value, and the consent constraint follows immediately.

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 two-parameter mutation with annotations covering safety and no output schema, the description is nearly complete. The main gap is that it does not explain the required list and subscriber identifiers.

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 0%, so the description must compensate for the two required identifiers, but it does not mention list_uid or subscriber_uid at all. The parameter names are somewhat self-explanatory, but the description adds no guidance on what identifiers to supply.

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: set a previously unsubscribed subscriber back to subscribed. It distinguishes the operation from sibling tools like unsubscribe_subscriber and add_subscriber by making the prior unsubscribed state explicit.

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 gives a clear condition for use: only when the person asked to be re-added (consent). That also implies when not to use it, but it does not explicitly name alternatives such as update_subscriber or unsubscribe_subscriber.

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