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

Annotations already declare the write/destructive/idempotent profile, and the description adds real behavioral context: an approval step is required before creation, the retargeting-vs-destination-list rule, and that over MCP it runs immediately without a confirmation_token. It does not explain what the destructiveHint=true implies (what a draft creation can overwrite), which is the remaining gap.

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?

Purpose and the key constraints are front-loaded, and the procedural sentences (ask about type, delay, mode, template, final step) each carry usable instruction. It is dense but nearly every sentence earns its place; only slight redundancy between the description and schema on message_template variables.

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 mutation tool with no output schema and full schema coverage, the description covers approval flow, parameter resolution, defaults, and MCP invocation semantics, and states it 'returns the result'. The main omission is any explanation of the destructiveHint implication, which an agent would otherwise have to guess.

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 100%, so baseline is 3, but the description adds genuine meaning: the agent_id/list_id resolution logic (agent's destination list, else product default assigned to both), the default 4-step workflow when workflow_steps is omitted, the questions to ask for custom steps, and the allowed template variables. This goes meaningfully beyond the field descriptions.

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 ('Create a draft campaign') and immediately distinguishes scope with 'Never activate, discover, enroll, or send', which separates it from enable_campaign, create_agent, and similar siblings. An agent can identify this tool's role without opening the 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 explicit conditional guidance: with agent_id and no list_id use the agent's destination list; omitted workflow_steps yields the standard 4-step flow; custom steps require asking about type/delay/mode/template/final step. It also states the negative space ('Never activate, discover, enroll, or send') and the MCP invocation rule (call once, omit confirmation_token).

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