imap_reply_to_email

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

Even though no annotations are provided, the description discloses important behavioral traits: it automatically sets the recipient, prefixes the subject with 'Re:', preserves In-Reply-To/References threading, and always applies account defaultBcc. It does not mention whether the reply is actually sent immediately or saved as a draft, but the overall behavior is substantially transparent.

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 three sentences with no filler. It front-loads the core action, then adds the automatic behaviors, and finally gives routing guidance that directly helps tool selection. Every sentence carries 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 10-parameter tool with no output schema and no annotations, the description covers the key selection logic, automatic reply semantics, and defaultBcc behavior. It could mention the final disposition (whether the reply is sent immediately), but it is otherwise complete enough for an agent to invoke correctly.

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 every parameter already has meaningful documentation. The description adds some reply-specific context, such as what replyAll accomplishes, but it mostly relies on the schema for parameter meaning, which is appropriate at baseline.

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-plus-resource structure: 'Reply to an existing email identified by folder + uid'. It clearly distinguishes itself from the sibling imap_send_email by stating the automatic reply behaviors (recipient, subject prefix, threading), so an agent can tell exactly what this tool is for.

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 gives explicit routing guidance: 'Use this instead of imap_send_email whenever the user is responding to a message already in a mailbox.' This directly names the alternative and states the condition that selects this tool, leaving no ambiguity about when to invoke it.

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