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

Annotations already cover the safety profile (not read-only, not destructive, closed-world, not idempotent), so the description is free to add real context: the operation only creates a draft and sends nothing, and a warming mailbox will surface a warning. It does not address that repeated calls are not idempotent and will create duplicate campaigns, which is the one behavioral trait left uncovered.

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?

Three short sentences, zero filler, and the most decision-relevant fact (nothing is sent) is front-loaded in the first sentence.

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 non-destructive creation tool with annotations present and no output schema, the description covers the draft semantics, templating, and mailbox behavior well. The remaining gap is that it never says what comes back (presumably a campaign id needed for start_campaign/update_campaign), and no output schema exists to fill that in.

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 coverage is 50%, so the description must compensate, and it does for the two most semantically loaded parameters: emails support {first_name}/{company}/any contact field merge tokens, and mailboxes accept any connected mailbox. It says nothing about name or daily_limit, the latter of which the schema at least documents as per-mailbox-per-day.

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 and resource plus the crucial scope qualifier: a draft campaign where nothing is sent. That qualifier implicitly separates it from start_campaign and update_campaign without the agent needing to inspect either schema.

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 useful preconditions (a connected mailbox is needed; a warming mailbox produces a warning), which is implied usage guidance. However, it never says when to prefer this over siblings like update_campaign or start_campaign, or that a draft must later be started, so the routing decision is left to inference.

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