Apply a label

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

The description adds 'The message stays where it is,' which clarifies that the tool does not move the message—information not contained in the annotations. This is a useful behavioral detail beyond the non-destructive and idempotent hints already provided.

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, action front-loaded with no wasted words. Every word earns its place, and the structure is easy to scan.

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 description covers the core operation but lacks guidance on alternatives, prerequisites (e.g., label must exist), and potential error conditions. Given the tool has 5 parameters and no output schema, this is minimally adequate but not comprehensive.

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 80%, so the schema already carries most parameter documentation. The description itself adds no parameter-specific meaning, staying at the baseline expected when 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?

Clearly states the action 'Tag a message with an existing label' with a specific verb and resource. It distinguishes from related tools like move_to_folder by noting the message stays in place, making the purpose unambiguous.

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 explicit guidance on when to use this tool versus alternatives such as bulk_apply_label or remove_label. The note that the message stays provides a contrast to moving, but it does not tell the agent when to choose this over sibling tools.

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