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

The description adds substantial behavioral detail beyond annotations: it leaves line_inbox pending, stops the no-reply alarm, requires the lease-holding cable, stamps the skip with cable and epoch, and preserves prior replies. These are meaningful side effects and constraints for a mutation tool whose annotations already indicate it is non-readonly, idempotent, and non-destructive.

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 front-loaded with the core action and then layers behavioral details in a logical order. Every sentence contributes distinct, useful information without repetition, and the overall length is appropriate for a two-parameter mutation tool.

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 that annotations cover safety traits and the input schema is fully documented, the description completes the picture by explaining side effects, lease requirements, and interaction with existing replies. With no output schema, no return-value explanation is needed, and the behavioral scope is sufficiently 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 coverage is 100%, so both message_id and reason are fully described in the input schema. The description does not add meaning beyond the schema for these parameters, making the baseline score of 3 appropriate when the schema carries the parameter semantics.

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 states a specific verb and resource: 'Mark an incoming message of the line as handled without a reply'. It clearly distinguishes this from replying tools by emphasizing 'without a reply' and mentions the line_inbox state, making it identifiable among siblings like line_send and line_inbox.

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?

It provides clear when-to-use context with examples such as spam, duplicate, or answered elsewhere, and explains that already-answered messages remain answered. However, it does not explicitly name alternatives like line_send or line_inbox for different scenarios, leaving some inference to the agent.

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