list_folders

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

Annotations already declare readOnlyHint=true and idempotentHint=true, so safety is covered. The description adds behavioral context by specifying that the tool returns 'all' folders and explicitly includes system folders, which goes beyond the annotations and clarifies the expected scope of results.

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?

A single, concise sentence that front-loads the action and includes relevant specifics (inclusion of system folders). Every word serves a purpose; no redundant or filler content.

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's simplicity (no parameters, no nested objects), the description is fully adequate. It states what the tool returns and the presence of an output schema covers the return value structure, so no further detail is needed.

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 zero parameters, so schema coverage is 100% vacuously. The description adds meaningful context about the output scope ('all folders', 'including system folders'), though this pertains to output rather than parameters. Baseline for no-parameter tools is 4, and the description does not need to explain parameter meaning.

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?

Description clearly states the action: 'List all folders' with a specific resource (Proton Mail account folders). It further specifies inclusion of system folders like INBOX, Sent, Archive, which distinguishes it from sibling tools that list other entity types (e.g., list_emails, list_attachments). The verb and resource are unambiguous.

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 makes clear that this tool is for retrieving the complete folder hierarchy, including system folders. This implicitly differentiates it from list_emails and list_attachments, but it does not explicitly state when not to use it or mention alternatives. The context is clear enough for a well-scoped listing tool.

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