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

Annotations only declare destructiveHint=false and a title, so the description carries most of the behavioral load. It adds real value beyond the annotations by disclosing the required gmail.modify scope and the reconnect hint for accounts connected before the feature existed, plus the multi-account condition. It omits duplicate-name behavior or error cases, so not a 5.

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?

Three short sentences, front-loaded with the core action, then the auth requirement, then the multi-account condition. No filler and every sentence carries operational information.

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?

Auth scope, multi-account handling, and account selection are all covered, which is what an agent needs to invoke this successfully. No output schema exists, yet the description does not say what a successful call returns (e.g., the created label's id), a minor gap for a create operation.

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 schema already documents all four parameters including the enum options. The description's 'Pass account when more than one Gmail account is connected' reinforces the account parameter but adds no syntax or format detail beyond what the schema provides; baseline 3 is appropriate.

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?

States a specific verb and resource: 'Create a new Gmail label.' An agent can immediately tell this makes a new label rather than editing or removing one. It does not explicitly name siblings like update_label or delete_label, so it lands just short of the top mark.

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 prerequisite/context guidance ('Needs gmail.modify', reconnect hint, 'Pass account when more than one Gmail account is connected') but never states when to use this versus update_label (e.g., what to do if the label already exists) or any other alternative. Usage is implied rather than spelled out.

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