List Messages

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false. The description adds key behaviors: cursor-based pagination, no full body fetch, and attachment metadata includes a short-lived download_url, which goes beyond 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?

Single sentence that is dense with information: scanning, no full bodies, cursor pagination, filter categories, attachment metadata. No wasted words, front-loaded with the main action.

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 large parameter count (24) and existing output schema, the description covers the essential use case and notable feature (short-lived download URL). Could mention pagination cursor behavior slightly more, but overall adequate.

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% with descriptions for all 24 parameters. The description provides a high-level overview of filter types (folder_id, keyword, dates, etc.) but does not add semantic depth beyond the schema. Baseline 3 is appropriate.

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 explicitly states the tool's purpose: 'scan mailbox messages by cursor without fetching full bodies.' It clearly distinguishes from sibling tools like mailbox_get_message, which fetch full bodies, and lists filtering capabilities.

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 when to use (scanning/listings without full bodies) and provides filtering context. However, it does not explicitly state when not to use or mention alternatives like mailbox_get_message or mailbox_batch_get_messages.

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