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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint=false, so the safety profile is covered. The description adds real behavioral context beyond that: the default and hard cap of 100 results, and the requirement to use pagination.next_offset for subsequent pages. It does not state result ordering outside the folder case or any rate limits, keeping it below a 5.

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 compact sentences with zero filler, front-loaded on the primary verb and pagination constraint, then the disambiguating sibling reference. Every clause carries information the 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?

An output schema exists, so return values need not be explained, and the description still supplies the key pagination contract (next_offset). With a 7-parameter schema fully documented and required mailbox_id clear, the definition is close to complete; only the query+folder interaction and result ordering are left implicit.

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%, so the schema already documents limit, query, folder, offset, account_id, and reason in detail. The description largely restates those semantics ('query searches file names/paths; folder lists immediate files') without adding format or edge-case detail beyond what the schema provides, so 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 states a specific verb and resource ('List mailbox files') and immediately scopes it with pagination bounds. It also explicitly separates this tool from mailbox_email_list, so an agent can distinguish it from the closest sibling without opening either 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?

It tells the agent when to use this tool versus mailbox_email_list ('Use mailbox_email_list for received emails') and explains how to continue paging via pagination.next_offset. It lacks guidance on when to prefer mailbox_file_get or how query and folder interact when combined, so it falls short of full when/when-not coverage.

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