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

The description goes far beyond the annotations. It discloses that the folder is automatically subscribed, that '/' builds hierarchy rather than appearing literally, that the operation is idempotent with case-insensitive matching, that the reply indicates whether something was created, and that blank path segments are refused. This is exactly the kind of behavioral context an agent needs.

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 dense but every sentence earns its place. It front-loads the core purpose, then covers hierarchy, idempotency, parent constraints, and validation rules in a logical order. The length is justified by the number of non-obvious behaviors an agent must know to call the tool correctly.

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?

Despite having no output schema, the description tells the agent what the reply indicates ('whether it actually created anything'), covers error conditions (blank segments), explains idempotency, and clarifies the relationship with list_mailboxes via selectable: false. The tool is fully specified for correct invocation.

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%, but the description adds substantial meaning beyond the schema. It explains the literal-slash prohibition, the case-insensitive matching behavior, the parent parameter's role with non-selectable folders, and the refusal of blank segments. This transforms the parameters from simple strings into well-understood inputs.

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 opens with a specific verb and resource: 'Create an IMAP folder.' It clearly distinguishes this from sibling tools like delete_folder and rename_folder by focusing on creation semantics, and adds concrete details about namespace rules and subscription behavior that make the tool's purpose unmistakable.

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 gives strong contextual guidance: it explains when to use the parent parameter, how slash-based hierarchy works, and that creating under a non-selectable parent is the intended way to make it a real folder. It does not explicitly name alternatives or say 'use this instead of X,' but the sibling list and clear creation focus make the intended use obvious.

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