apply_label

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 but does not say whether the label replaces existing labels, whether the label must already exist, or what side effects or errors might occur. This is too opaque for a mutation tool.

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?

A single, front-loaded sentence with zero filler. Every word contributes to stating the operation clearly, making it easy to parse quickly.

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 schema covers parameter semantics, including the mailbox caveat, but the description lacks usage guidelines and behavioral details. For a simple labeled action this is minimally viable, but it leaves gaps around when to use it and what the operation actually does beyond the literal statement.

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 100%, so the input schema already documents all three parameters. The description adds no additional meaning about uid, label, or mailbox beyond what the schema states, which meets the baseline but does not exceed it.

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 identifies a specific verb and resource ('Apply a label to an email'), making the operation clear at a glance. It does not explicitly differentiate from siblings like list_labels or get_emails_by_label, but the action semantics are distinct enough that an agent can infer which tool to use.

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?

No guidance is given on when to use this tool versus alternatives such as star_email or mark_as_read. The only contextual clue about mailbox requirements appears in the input schema, not the description, leaving selection criteria entirely to the agent's inference.

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