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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior, so the description's burden is lower. It adds useful behavioral context beyond annotations: the return shape is compact summaries with fields like read status and attachment flag, and the default folder is inbox. No contradiction with annotations was found, though sorting/pagination behavior is not disclosed.

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?

Three tight, front-loaded sentences: the first states the action and default folder, the second states the output shape and supported filters, and the third states when to use it. There is no filler, repetition, or unnecessary detail.

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 read-only browse tool with 4 fully documented parameters and strong annotations, the description covers folder scope, filters, and return-shape information despite the absence of an output schema. It is not a 5 because it omits sort order and pagination behavior, and it does not explicitly route advanced search needs to outlook_search_messages.

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?

The schema documents 100% of the parameters (top, folder, search, unread_only), so the schema already carries the heavy lifting. The description paraphrases the search and unread-only filters and mentions the inbox default, but it does not add meaningful semantic detail beyond the schema, keeping this at the baseline 3.

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 and resource: 'List email messages from an Outlook / Microsoft 365 mailbox folder' and clarifies the output is compact summaries. It is clearly distinguishable from sibling tools like outlook_get_message and outlook_search_messages, though it does not explicitly name those alternatives to earn a 5.

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 closes with an explicit intended use: 'Use to browse a user's Outlook email.' This gives clear context for when the tool is appropriate, but it does not say when not to use it or how it compares to the sibling outlook_search_messages, so it falls short of full alternative routing.

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