reply_to_email

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It does not mention any side effects (e.g., sending the reply, modifying the thread), permissions required, potential errors, or rate limits. For a mutation tool, this is a noticeable gap.

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, front-loaded sentence that efficiently conveys the tool's core purpose. Every word contributes meaning, with no redundancy or unnecessary detail.

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 tool is simple, with a fully documented schema and no output schema needed. The description, while brief, covers the essential input requirement (original email ID) and the action. Given the low complexity, this is reasonably complete, though it could benefit from a note about expected behavior or usage context.

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?

The input schema covers 100% of the parameters with clear descriptions. The tool description does not add significant meaning beyond the schema, merely restating the 'original ID' concept. Baseline 3 is appropriate since the schema already documents the parameters well.

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: replying to an existing email thread using its original ID. It distinguishes itself from siblings like send_email (which sends new emails) and read_email (which retrieves content). The verb+resource structure is specific and 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?

The description implies the tool should be used when the user wants to reply to an existing thread, as opposed to creating a new email. However, it does not explicitly mention when not to use it or provide alternatives, leaving the usage context implied rather than explicit.

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