Mark a message

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

Annotations already declare readOnlyHint false, destructiveHint false, and idempotentHint true, covering the safety profile. The description adds no extra behavioral context about side effects, confirmation needs, or error behavior beyond the action itself.

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?

One sentence, front-loaded with the action, and no redundant words. It is appropriately concise for the tool's straightforward functionality.

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?

Given the tool has 5 parameters including dry_run and uidvalidity safety mechanisms, the description is quite terse. However, schema descriptions fill in those details, and the annotations provide safety context, making the description minimally acceptable.

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 covers 60% of parameters with descriptions (folder, dry_run, uidvalidity). The description restates the action enum but adds little for uid or the purpose of dry_run, though the schema fills those gaps adequately.

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 marks a single message with read/unread or star/unstar actions. The singular 'a message' distinguishes it from bulk_mark and other batch operations, and the action set differentiates it from label/move tools.

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?

Usage is implied: use this when you want to mark one message's state. However, it does not explicitly mention alternatives like bulk_mark for multiple messages or provide when-not-to-use guidance.

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