assistantmail_reply_message

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

No annotations are provided, so the description is the only source of behavioral information. It only nods that a reply is being performed, but does not disclose any side effects, return behavior, or authentication requirements (apiKey). This is a thin disclosure for a mutating tool operating on a mailbox.

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 entire description is one clear sentence with no filler or redundant details. Every word earns its place, and the key intent (replying to existent message in a thread) is front-loaded and complete.

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?

With five parameters, no output schema, and no annotations, the description is insufficient to fully understand how to invoke the tool. It does not explain required vs optional parameters, how the response is returned, or any prerequisites such as the apiKey format. More context is needed to reliably call the tool beyond just guessing its purpose.

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 has 0% description coverage and the tool description does not clarify any parameter's purpose. The word 'message' hints at messageId, but html, text, apiKey, and mailboxId remain completely unexplained. The description provides almost no compensation for the missing schema metadata.

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 action 'replies' and the target 'existing message in a mailbox thread.' This distinguishes it from sibling tools like send_email, which creates a new email, and get_message, which only reads. It is not a tautology and leaves no ambiguity about what the tool does.

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 when to use the tool (when replying to an existing message) but provides no explicit when-not to use it or alternatives. It does not address how it differs from send_email or when a reply is not appropriate. A clear implication is present, hence the middle score.

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