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

Annotations already mark the tool as read-only and idempotent. The description adds valuable context: API keys are never returned, and connecting happens in the app (not through this tool). These security and setup details go beyond the annotations.

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 a single, dense sentence that packs essential info: channel types, examples, cross-reference to send_email, approval status, setup location, and security note. Each part earns its place, though it could be split into two sentences for readability.

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 no output schema, the description adequately explains what is returned (connected channels and approval status). It also mentions the mailbox_id usage for send_email, which is a practical integration detail. It doesn't describe the exact return format or pagination, but for a simple list tool this is sufficient.

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?

The tool has no parameters, so the description has nothing to explain about them. Baseline for zero parameters is 4, and the description correctly focuses on the output and purpose without needing parameter coverage.

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 tool lists connected email channels, specifying the two types (sequencers like Smartlead/Instantly and user mailboxes via Outlook/IMAP). It also notes additional info about manual approval. This distinguishes it from sibling tools like list_email_campaigns and send_email.

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 implies usage for checking connected channels before sending emails, and explicitly instructs how to use the mailbox_id in send_email. However, it doesn't explicitly exclude alternatives or state when not to use it, but the context is clear enough.

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