list_emails

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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description aligns with this by describing a read-only listing operation. It adds valuable behavioral details beyond the annotations: paginated results, metadata (with icons), and the ProtonMail-specific behavior where labels are represented as IMAP folders — a non-obvious nuance that helps agents avoid pitfalls.

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?

Three sentences, each purposeful: the first states the core function and return type, the second points to a sibling for a specific need, and the third offers a platform-specific tip. No filler or repetition.

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 tool with 12 parameters and no output schema, the description covers the essential aspects: listing with filters, paginated results, metadata, and a critical platform-specific caveat. It doesn't fully address differentiation from search_emails or output structure, but the schema and sibling names fill those gaps. It is sufficiently complete for an agent to decide when and how to use it.

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 schema covers 100% of parameters, so baseline is 3. The description adds extra meaning by providing a concrete usage example for the mailbox parameter (mailbox='Labels/X'), showing how ProtonMail labels map to folders. This goes beyond the schema's generic 'Mailbox path (default: INBOX)' and enriches understanding of the filter behavior.

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 'List emails in a mailbox with optional filters' — a specific verb and resource that immediately conveys the tool's function. It also distinguishes itself from related tools by directing users to 'get_email' for full body content, and the mention of metadata (read/unread, flagged, replied, attachments, labels) adds further scope clarity.

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 provides explicit guidance: use get_email for full body content, and for ProtonMail labels use list_labels then list_emails with mailbox='Labels/X'. This gives clear context for when to use the tool versus alternatives, though it doesn't explicitly contrast with search_emails or other sibling list tools.

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