reply_message

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

With no annotations, the description carries the full burden of behavioral disclosure. 'Reply' implies sending a response, but the description does not state whether this sends immediately, how it handles threading, whether attachments are carried over, or what side effects occur.

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 clear sentence with no filler. The essential action is front-loaded and every word contributes to the meaning.

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 4-parameter tool with no annotations, no output schema, and no parameter descriptions, a single purpose statement is not enough. The agent lacks guidance on optional recipients, mailbox selection, comment handling, and the tool's relationship to reply_all_message.

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 0%, so the description should compensate by explaining the parameters. It does not. The core parameter message_id is implied by 'sender of a message', but comment, mailbox, and extra_to are left entirely unexplained.

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 uses a specific verb ('Reply') with a clear resource ('the sender of a message'). It immediately differentiates this tool from siblings like reply_all_message, forward_message, and send_message by anchoring the action to the original sender.

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?

No guidance is given about when to choose this tool over reply_all_message, forward_message, or create_draft. There are no exclusions, alternatives, or contextual conditions, leaving the agent to infer usage purely from the tool name and sibling list.

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