reply_email

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

With no annotations, the description carries the full burden and does disclose meaningful automatic behavior: 'Re:' prefix handling, In-Reply-To/References headers, recipient selection, and quoting the previous message. It stops short of stating that the reply is actually sent, any auth requirements, or irreversibility, which keeps it from a 5.

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 sentences, zero waste, with the core action front-loaded and the automatic-handling details following. Every clause earns its place.

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?

Output schema exists so return values need not be explained. For a mutation tool with no annotations, the description covers the reply-construction behavior well, but omits whether the message is dispatched immediately and any permission requirements, leaving a small gap.

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 100%, so all six parameters (including folder default, reply_all, attachments) are already documented in the schema. The description's mention of 'recipient selection' loosely relates to reply_all but adds no syntax or format detail beyond the schema, so the baseline of 3 applies.

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?

States a specific verb (reply) and resource (existing email message), which clearly differentiates it from send_email and forward_email in the sibling list. Missing an explicit sibling contrast, but the action is unambiguous.

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?

Usage is implied by 'reply to an existing email message' — an agent can infer this is for responding to a received message rather than composing or forwarding one. However, no explicit when-to-use guidance or comparison to send_email/forward_email is provided.

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