reply

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

No annotations are provided, so the description must disclose behavioral traits. It only mentions the scope of the reply ('original sender only'), but omits critical aspects such as the side effect of sending an email, any permission requirements, behavior regarding attachments/HTML, or how the reply interacts with the email thread. This is insufficient for a mutation tool with zero annotation support.

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 that states the action and scope without any filler or redundant information. It is appropriately concise for a simple tool.

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?

The tool has no annotations, no output schema, and is a side-effecting operation. The description covers the core purpose but lacks context on when to choose this over 'send_email', whether the original message is quoted, or what the agent should expect as a response. It is adequate for basic understanding but incomplete for robust agent decision-making.

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 provides descriptions for 100% of the parameters, so the description does not need to add param-level details. The baseline score of 3 applies because the schema already documents 'id', 'body', 'html', and 'attachments' adequately, and the description adds no additional parameter semantics.

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's function: 'Reply to the sender of an email', with the parenthetical '(reply to original sender only)' further specifying scope. This distinguishes it from the sibling tool 'reply_all', which is present in the sibling list.

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 provides an explicit scope ('original sender only'), which implies when to use this tool versus 'reply_all'. However, it does not explicitly name alternatives or discuss when to use 'send_email' over 'reply'. The context is clear for the reply vs reply-all distinction but lacks broader usage guidance.

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