Compose Email

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

The annotations already convey this is a mutating, non-idempotent operation. The description adds a meaningful behavioral detail beyond the schema: the inbox signature is appended automatically, and it is placed above quoted text on replies and forwards. This helps the agent predict side effects and know when to set include_signature to false.

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 compact, front-loaded sentences with no filler. The first sentence states the core operations; the second provides the one behavioral caveat an agent most needs before composing replies or forwards.

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 17 parameters and conditional schemas, the description gives the essential high-level shape while the input schema covers details like inbox selection, attachments, idempotency, and recipient limits. The only notable omission is any mention of return values, but no output schema is provided and the tool's success/failure behavior is largely inferable.

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 the schema already documents all 17 parameters thoroughly. The description adds only a small nuance about signature placement relative to quoted text; it does not substantially enrich parameter understanding beyond the schema 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 names specific actions ('Send new mail, reply, or forward') and a clear resource ('from one inbox'). These verbs distinguish it sharply from sibling tools like email_read, email_delete, and email_organize, so an agent can select it without opening the schema.

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 clearly establishes the use case: any time the user needs to send, reply to, or forward email. It does not list alternatives or explicitly say when not to use this tool, but the context is unambiguous enough and clearly separated from the sibling read/delete/organize operations.

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