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

Annotations already declare destructiveHint=true, idempotentHint=false, and openWorldHint=true, so the safety profile is covered. The description adds genuine non-annotation context: trash/untrash are supported but permanent deletion is not available for Gmail OAuth, which prevents an agent from attempting an impossible operation. It still omits what 'move' does to a message and what the call returns.

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?

Two short sentences, zero filler. The operation scope is front-loaded and the limitation follows immediately.

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 destructive, open-world mutation with an enum-driven action set and no output schema, the description covers the operation surface and one important platform limitation. It leaves gaps on account selection, batch limits, action/parameter pairing, and result reporting, which the totally undescribed schema does not fill in.

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% across 5 parameters, so the description must compensate and largely does not. It gestures at labels and folders, but says nothing about messageIds (required, 1-100 items), accountId (relevant given the sibling list_accounts), or which action values require which companion parameters.

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?

States a specific verb and resource ('Change message flags, labels, or folders') that maps cleanly onto the action enum and the folder/labels parameters. An agent can tell it apart from list_emails/get_email, but it does not explicitly differentiate itself from update_draft or delete_draft.

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?

Usage is implied by the mutation verb, and the second sentence gives one real constraint (permanent deletion unavailable on Gmail OAuth). However, there is no explicit statement of when to prefer this over siblings like delete_draft, nor any prerequisite (e.g., label/folder must pre-exist) for move/addLabels actions.

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