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

Annotations already declare readOnly, idempotent, non-destructive, so the safety profile is covered. The description adds value beyond that by disclosing what the result contains: stage-by-stage conversion rates, the largest drop-off point, and prescriptive recommendations — important because there is no output schema.

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, zero filler, with the core purpose and the funnel stages front-loaded before the analytical extras. Every clause earns 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?

For a single-parameter read tool with full annotation coverage and no output schema, the description does the necessary work of describing what is returned. It stops short of stating behavior for an unsent or invalid campaign, which is the only notable gap.

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?

With one parameter at 100% schema coverage, the schema already documents campaign_id fully, giving a baseline of 3. The description contributes a small amount of extra meaning by specifying the campaign must be a 'sent' campaign, narrowing what IDs are valid, but offers no error or format guidance.

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 names a specific action and resource — visualize the engagement funnel for a sent campaign — and enumerates the exact stages (sent → delivered → opened → clicked). This is clearly distinguishable from sibling reporting tools like get_campaign_opens or analyze_campaign, though it never names those siblings explicitly.

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 phrase 'for a sent campaign' implies a precondition (the campaign must already have been sent), which is useful context. However, there is no explicit statement of when to prefer this over analyze_campaign, campaign_health_dashboard, or compare_campaigns, so the agent must infer the choice.

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