Reply to email

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It usefully reveals that it modifies threading headers and subject, but it does not state that it sends an email on behalf of the authenticated account, any irreversible side effects, or what the tool returns. This is a meaningful gap for a sending-like mutation tool.

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 two sentences with no filler. The core action is front-loaded, and the threading/subject behavior is stated in the second sentence without unnecessary elaboration. Every sentence earns its place.

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 with 9 optional parameters and no output schema, the description covers the main purpose and important threading behavior but omits return values, send-side effects, and body/recipient expectations. An agent can likely invoke it correctly for a simple reply, but several edge behaviors remain implicit.

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 56%, so the schema already documents several parameters such as uid, folder, reply_all, message_id, and attachments. The description adds value by explaining why uid/message_id matter and how threading works, but it does not clarify un-described parameters like cc, bcc, html, or text. It provides useful but incomplete parameter context.

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 opens with a specific verb and resource: it replies to a received message identified by uid or message_id. It also adds distinguishing detail about thread preservation through In-Reply-To/References and subject prefixing, which clearly separates it from sibling tools like send_email.

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 clearly establishes the intended use case: replying to an existing received message rather than composing a new one. It does not explicitly name alternatives or state when-not-to-use, but the context is clear enough for an agent to select it over send_email for threading-aware replies.

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