applyGmailMessageLabels

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states the action (adds/removes labels) but does not disclose important traits such as reversibility, permission requirements, idempotency, or what happens on invalid input. As a mutation tool, this lack of safety or side-effect information is a significant gap.

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 two concise sentences, front-loaded with the core purpose and immediately followed by useful context. Every word earns its place with no redundancy or filler.

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?

The tool is simple with well-documented parameters, but the description omits any mention of return values, prerequisites (e.g., label IDs must come from listGmailLabels), or behavior when both add and remove are specified. It is adequate for basic usage but not fully complete given the lack of an output schema and annotations.

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 schema covers 100% of the parameters with descriptions. The tool description adds no additional meaning beyond what the schema already provides—it simply restates the add/remove concept without explaining parameter relationships or edge cases. Baseline 3 is appropriate because the schema does the heavy lifting.

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 the tool's function with a specific verb and resource: 'Adds or removes labels from a Gmail message.' It also narrows the scope by mentioning drafts, sent emails, or any existing message, which distinguishes it from sibling tools like sendGmailEmail or listGmailThreads.

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 provides clear context on when to use this tool: 'This can be used to label drafts, sent emails, or any existing message in the user's Gmail account.' It does not explicitly mention alternatives or exclusions, but the context is sufficient for a simple label-modification operation.

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