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

With no annotations, the description carries the full burden of behavioral disclosure. It lists the actions but does not disclose potential side effects (e.g., trash may be irreversible, add_label requires a labelName), permissions needed, or reversibility. For a mutation tool, this is a significant gap in transparency.

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 a single sentence with no redundant words. It efficiently communicates the core scope and is front-loaded with the key information. It earns a high score for conciseness despite omitting details, which is penalized elsewhere.

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?

For a tool that mutates email state, this description is too sparse. It lacks prerequisites (e.g., messageId from a prior search), the labelName requirement for add_label, and any behavioral expectations. There is no output schema, and annotations are absent, so the description is not complete enough for a simple but mutable tool.

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 0%, and the description does not compensate. It never mentions messageId or labelName, nor does it specify that add_label requires labelName. The action enum values are the only hints, but parameter semantics are entirely delegated to the schema, which is insufficient.

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 ('Mark') and a specific resource ('Gmail email'), enumerating all supported actions (read/unread, archive, trash, add_label). This distinguishes it from siblings like send_email, forward_email, and outlook_email_action, which have different purposes. The verb 'Mark' is slightly imprecise for archive/trash/add_label, but the overall intent is unmistakable.

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 implies usage: when you want to modify a Gmail email's state. However, it provides no explicit guidance on when to use this tool versus alternatives, such as outlook_email_action for Outlook, or search_email first to obtain a messageId. No exclusions or prerequisites are mentioned, so usage context is only implied.

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