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

Annotations indicate readOnlyHint=false, so this is known to be a write operation. The description adds valuable behavioral context beyond annotations: sender auto-resolution logic, the prompt-to-choose fallback, and the reply-to default behavior. It does not disclose all post-creation behaviors (e.g., whether a draft is created without is_publish), but the critical decisions are surfaced.

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?

The description is three concise sentences. The first states the purpose, the second states required fields, and the third explains important default behaviors. No filler words; every sentence earns its place. Structure is logically ordered from general to specific.

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?

Given the tool has 20 parameters and no output schema, the description covers the most critical creation logic (required fields, sender resolution, reply-to default). It does not mention response format or error handling, but the schema covers all parameter meanings and annotations cover safety. The description is complete enough for correct invocation in most scenarios.

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 every parameter already has a description. However, the description significantly enhances understanding of key parameters (sender_name, sender_email, sender_id, reply_email, reply_id) by explaining fallback and default semantics. This is exactly the kind of added meaning that helps an agent choose and fill parameters correctly.

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 clearly states the specific action 'Create a new email campaign in MailerCloud'. It names the resource (email campaign) and the required inputs, distinguishing it from sibling tools like update_campaign or list_campaigns. The verb 'create' is unambiguous and the context is explicit.

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 description gives explicit prerequisites (name, subject, list ID) and explains default behaviors for sender resolution and reply-to configuration. It does not explicitly compare against alternatives like schedule_campaign or send_transactional_email, but it provides enough context for an agent to know when to invoke this tool for creating a new campaign.

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