modify_gmail_message_labels

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

With no annotations, description carries full burden. It discloses side effects (mutates label set) and required OAuth scope (gmail.modify). Could add more on error handling or idempotency, but covers key behavioral traits.

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?

Five sentences, front-loaded purpose, then side effects, recipes, alternatives, and scope. Every sentence adds value; no waste.

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?

Covers all necessary context: usage boundaries, parameter specifics, side effects, permissions, and relationships to siblings. Output schema exists, so return values are handled.

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?

Adds significant meaning beyond schema: explains that label IDs must be system IDs or user label IDs (names do not work), and that message_id comes from search_gmail_messages. This prevents common mistakes.

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 clearly states 'Add or remove labels on one Gmail message', specifying verb and resource. It distinguishes from sibling tools like batch_modify_gmail_message_labels and manage_gmail_label, ensuring no confusion.

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?

Provides explicit guidance: use batch_modify_gmail_message_labels for bulk operations, use manage_gmail_label for creating/deleting labels. Also includes common recipes (archive, delete, star) and required OAuth scope.

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