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

readOnlyHint=true already establishes the safety profile, so the bar is lower; the description still adds value by disclosing the shape of the result (folder ids and message counts) in the absence of an output schema. It does not mention pagination, size limits, or per-account auth requirements, which keeps it out of the top band.

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?

Two sentences, zero filler, and the core purpose is front-loaded before the workflow hint. Every clause carries information an agent needs.

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 zero-required-param, read-only listing tool, the description covers what is listed, what comes back, the mailbox scope, and how the output feeds the downstream search tool. Nothing needed to invoke it correctly is missing.

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 100% and the single 'account' parameter already documents its email-address format and the omit-to-use-all default. The description adds no syntax or semantics beyond that, so the baseline of 3 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?

States a precise verb and resource ('List the mail folders in the user's connected Outlook mailboxes') and goes further by naming the returned fields (ids and message counts). An agent can distinguish it from list_outlook_calendars, list_gmail_labels and the search/read Outlook tools without opening a schema.

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?

Gives a concrete trigger ('when the user names one of their folders') and an explicit sequencing rule with the sibling it feeds ('before searching it with search_outlook_messages(folder=...)'). It covers when-to-use and the alternative, but no explicit when-not or scope caveats (e.g., multi-mailbox enumeration cost).

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