update-mail-message

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

Annotations already indicate destructiveHint=true and readOnlyHint=false, so the mutation nature is known. The description adds that certain fields (subject, body, recipients) are only editable for drafts, which is useful nuance. It does not mention other side effects like confirmation requirements or authorization needs, but the schema covers the confirm parameter. No contradiction with 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?

Single, well-structured sentence that front-loads the action and resource, then lists examples. No redundant terms or vague filler. Efficiently conveys the core purpose without unnecessary length.

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?

The tool has complex nested objects and many parameters, but the description gives enough to understand what it does and what fields are relevant. It lacks explicit details on limitations (e.g., sent messages cannot have body/recipients changed, requiring draft status) and does not mention the return format, though no output schema exists. For a mutation tool, it is adequate but not exhaustive.

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 80%, so the schema already documents most parameters. The description adds semantic examples (isRead, flag, categories, importance) that clarify what kind of updates are typical, but it does not explain the structure of the body object beyond that. It adds modest value over 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 verb and resource ('update an existing Outlook email message by its message ID') and lists concrete examples of what can be changed (read status, flag, categories, importance, draft content). This clearly distinguishes it from creation, sending, or deletion tools among siblings.

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 provides clear context for when the tool is appropriate (updating existing messages) and implies it is not for creation or sending. It does not explicitly name alternatives or state when-not-to-use, but the enumerated use cases (marking read/unread, flagging, editing drafts) give an agent enough to select it correctly.

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