list_labels

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

With no annotations, the description carries the behavioral burden. 'List' implies a read-only operation, and the description adds useful structural context that labels are IMAP folders under Labels/. It does not disclose details like account filtering or response behavior, but it offers enough for a simple list operation.

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 two concise sentences. The main purpose is front-loaded, and the second sentence adds a valuable routing note without any wasted words.

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?

The tool is simple, has an output schema, and the description covers its core purpose plus a useful link to list_emails. However, the account parameter is left unexplained, and with 0% schema coverage this is a small but real completeness 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?

Schema description coverage is 0%, and the description does not mention the 'account' parameter at all. The schema only provides the title 'Account' and a default of 'default', so the description adds no meaning beyond the structured schema. This is a clear gap.

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 starts with a specific verb and resource: 'List ProtonMail labels.' It also distinguishes labels from related concepts by noting they are IMAP folders under Labels/, and names the sibling list_emails for viewing tagged mail. This clearly separates it from list_mailboxes and list_emails.

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 explicitly tells the agent to use list_emails with mailbox="Labels/<name>" to see tagged mail, which is a concrete routing instruction. It does not explicitly state when not to use list_labels or contrast it with list_mailboxes, but the provided guidance is clear and actionable.

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