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

Annotations already establish this as a non-read-only, non-destructive, non-idempotent write. The description goes beyond them by disclosing the key behavioral fact that the resulting copy is inactive and auto-named 'Copy of ...', which materially affects what the agent does next. It stops short of stating permission requirements or that the source mailer is left unmodified.

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, zero filler, with the action stated first and the non-obvious outcome (inactive, auto-named copy) immediately after.

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?

An output schema exists and both parameters are documented, so the description only needs to explain behavior – which it does by covering the inactive state and naming convention. It could be slightly more complete by noting the follow-up path (edit then activate) or permission expectations, but nothing essential to invoking it is missing.

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%, so event_id (from search_events) and mailer_id are already fully documented, and the description repeats none of that. Given the high coverage baseline, a 3 is appropriate – the schema carries parameter meaning entirely.

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?

Uses a specific verb+resource ('Duplicate a mailer') and adds concrete detail about the result ('inactive copy named \'Copy of ...\''). It implicitly separates itself from create_mailer and duplicate_site_page, though it never names the adjacent create/update mailer tools an agent might confuse it with.

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?

Usage is implied: call this when you want a copy of an existing mailer rather than a new one, and the copy starts inactive. No explicit when/when-not statement, no mention of prerequisites such as obtaining event_id via search_events (that only appears in the schema), and no pointer to update_mailer or activate_mailer as follow-ups.

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