preview_send

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

readOnlyHint=true already declares the no-mutation safety profile, and 'without sending' reinforces it rather than adding new information. The word 'resolved' hints that recipients/from are computed (e.g., from replyToMessageId or send-as addresses), which is useful, but nothing is said about validation failures, auth requirements, or what happens with invalid addresses.

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?

A single tight sentence that front-loads the verb and outcome, with zero filler. Everything it says 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?

For a 12-parameter, zero-required tool with an output schema and rich schema descriptions, the message is conveyed. It could go further by explaining how draftId and replyToMessageId interact with the preview, but the structured fields and output schema carry most of that burden.

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 83%, so the schema already documents nearly every parameter, including draftId, replyToMessageId, accountId, and the attachment object shape. The description adds no parameter-level detail beyond the field list, so the baseline 3 for high schema coverage 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?

The description uses a specific verb ('Show') plus a concrete resource set (resolved sender, recipients, subject, attachments) and adds the crucial qualifier 'without sending', which cleanly separates it from send_email. It does not explicitly name send_email or forward_email as the sending siblings, so it falls just short of full sibling differentiation.

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 only implied: 'without sending' suggests a dry-run preview before send_email, but the description never states when to prefer this over composing a draft (create_draft) or sending directly. No explicit when/when-not or named alternative is given.

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