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

Annotations already declare readOnlyHint=false, destructiveHint=false and idempotentHint=false, so the safety profile is covered structurally. The description adds the useful precondition that the mailer must be active, but says nothing about consequences (does it stop queued sends?), reversibility (can it be reactivated via activate_mailer?), or the failure mode when the mailer is already inactive.

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 short sentences, front-loaded, with the constraint immediately after the action statement. The first sentence is essentially a restatement of the tool name/title, so a small amount of the text is redundant rather than earning 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?

The tool has only two fully documented required parameters, an output schema, and annotations covering safety, so the description does not need to explain returns or parameters. The remaining gap is behavioral: it does not say what deactivation does to the mailer's scheduled sends or how to undo it.

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%: event_id is documented as coming from search_events and mailer_id as the mailer UUID, so the schema carries the parameter burden. The description adds no syntax, format, or scoping detail beyond that, making the baseline 3 correct.

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+resource ('Deactivate a mailer') that clearly pairs against the sibling activate_mailer and is distinct from delete_mailer. It stops short of naming those siblings explicitly, so the differentiation is inferred from the verb rather than spelled out.

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 precondition 'Only allowed when the mailer is currently active' is a real usage constraint, but it is a state gate rather than guidance on when to choose this over alternatives such as delete_mailer or update_mailer. No exclusions or alternative-selection advice is offered.

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