reply_email

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

With no annotations, the description carries the disclosure burden. It reveals key behaviors: automatically fetching the original email, building threading headers, and defaulting to immediate sending with a draft option. It could mention return values or error handling, but the main side-effects are covered.

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?

Two concise sentences, front-loaded with the core action and key behavior. No wasted words, and every phrase adds useful information.

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 10 parameters and no output schema, the description provides a solid workflow overview (reply, fetch original, threading, send/draft). The rich schema already documents parameters, so this level of description is adequate, though it could include a note about return values if relevant.

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 coverage is 100%, so the description doesn't need to explain every parameter. It adds modest value by emphasizing the originalEmailId and send behavior, but these are already in the schema. The description doesn't significantly enhance parameter understanding beyond the schema.

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 replies to an existing email, specifies threading headers (In-Reply-To, References), and notes automatic fetching of the original email. This distinguishes it from sibling tools like send_email, create_draft, and send_draft.

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 explains the default behavior (sends immediately) and how to save a draft instead (send=false), giving clear usage context. It doesn't explicitly name alternatives or exclusions, but the scope is clear enough for an email reply tool.

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