gmail_modify_labels

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

Annotations already indicate non-read-only, idempotent, and non-destructive behavior, but the description adds meaningful side-effect disclosure: removing INBOX archives and removing UNREAD marks read. It also lists the system labels, which is useful operational context beyond the schema and annotations.

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 compact and front-loaded with the core action. The system-label list and side-effect notes earn their place, and the Args block is appropriately brief. There is no filler or redundant repetition of the title.

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 relatively simple three-parameter tool with an output schema and informative annotations, the description covers label semantics and important side effects. Minor gaps remain, such as behavior when neither add nor remove is provided and the exact format of label ids, but they are not critical given the output schema and sibling context.

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 input schema has no property descriptions, and the Args section only partially compensates. 'add' and 'remove' mirror the parameter names with little added depth, while message_id is described only as 'Message to file,' which is imprecise. Optionality and label-id formatting are also left unspecified.

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: 'Add or remove labels on a message.' It then clarifies system labels and key side effects, making the tool clearly distinguishable from archive, mark-read, and trash siblings.

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 clear context for when label modification is appropriate and explicitly maps behaviors to alternatives: 'Removing INBOX archives a message; removing UNREAD marks it read.' It does not explicitly name sibling tools or state when not to use it, but the context is strong enough for an agent to route correctly.

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