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

Annotations only indicate non-read-only and non-destructive, so the description carries the burden of explaining behavior. It adds useful context: the email must be queued, attachment IDs come from list_attachments, and the same file can be attached to multiple emails. It does not contradict annotations.

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 compact, front-loaded with the core action, and every sentence adds value. The consent guardrail and parameter sourcing notes are included without unnecessary filler.

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 two-parameter tool with complete schema coverage, the description provides enough context to invoke it correctly: when to attach, what target emails qualify, and where the attachment ID comes from. It does not describe error behavior or the result of attaching to a non-queued email, but those gaps are minor.

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 schema already documents both parameters. The description slightly enriches recipient_email by clarifying the email must be pending or awaiting approval and attachment_id by tying it to list_attachments, but most parameter meaning is already in 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 states a specific action — attaching a file from the user's library to a queued outreach email — and clearly distinguishes this from sibling tools like detach_from_outreach or get_email_attachment. The verb, resource, and target are all explicit.

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 strong usage guidance: only attach when the user explicitly asks, never on the tool's own initiative, and only to queued emails (pending or awaiting approval). It does not explicitly name an alternative tool for the opposite operation, such as detach_from_outreach, so it falls just short of a 5.

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