Add File Attachment To Mail

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

With no annotations available, the description carries the disclosure burden. It adds useful behavioral details like the 3 MB decoded size limit and the permission requirement. However, it does not mention the return value, error conditions, or that the action modifies the draft, which would be expected for a complete behavioral profile.

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, with the core action in the first sentence, permission in the second, and a useful multilingual hint in the third. Every sentence adds value, and the structure is front-loaded with the primary purpose.

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 moderate-complexity tool with no output schema, the description covers the essential constraints (size, target, permission) and gives contextual intent phrases. It could be more complete by stating what the tool returns or what happens on failure, but it is sufficient for understanding the tool's primary function.

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 parameters are already well documented in the schema. The description's mention of 'base64-encoded file under 3 MB' aligns with the contentBase64 property description, but adds no new meaning beyond what the schema already provides. The baseline of 3 is appropriate.

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 'Add' and resource 'base64-encoded file to an existing draft message', clearly distinguishing this from sibling tools like mail_send_draft, mail_list_attachments, and calendar_add_file_attachment. It also provides Chinese intent phrases to aid recognition.

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 states the target context: adding a file to an existing draft message. It mentions the permission requirement (delegated Mail.ReadWrite) which helps agents know when the operation is allowed. However, it does not explicitly list alternatives or exclusions, such as not using this for calendar attachments.

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