assistantmail_reply_message

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

No annotations are provided, so the description must carry the full behavioral burden. It only says 'Replies,' but does not disclose whether the reply is sent immediately, saved as a draft, requires specific auth, or what the response looks like. This is significant for a mutating 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 a single, front-loaded sentence with no filler or redundancy. While it is somewhat under-specified for a full tool definition, its brevity and clarity on the basic action are strengths.

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 5 parameters, no annotations, and no output schema, the description is too thin to be fully actionable. It omits key operational details such as body format requirements, authentication expectations, and return behavior, leaving important gaps for an agent.

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%, and the description adds no parameter-level meaning. It does not explain the relationship between 'html' and 'text', the purpose of 'apiKey', or the exact roles of 'mailboxId' and 'messageId'. The agent is forced to infer everything from parameter names.

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 ('Replies') and resource ('existing message in a mailbox thread'), making the core action clear. It is distinguishable from siblings like assistantmail_send_email, which is for new messages, though it does not explicitly name the alternative.

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 phrase 'Replies to an existing message' implies the appropriate context for using this tool: responding within an existing thread. However, there is no explicit when-to-use guidance, no exclusions, and no mention of alternatives such as assistantmail_send_email.

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