list_messages

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, so the safety profile is covered. The description still adds two non-obvious behavioral facts the annotations do not: results are ordered newest first, and reading does not mark messages as read. It omits pagination/return-shape behavior, so not 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?

Two short sentences, zero filler, and the scope/ordering constraint is front-loaded before the side-effect note.

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 simple list tool with all-optional parameters and no output schema, the description covers scope, ordering and read-state side effects, and annotations cover safety. It is still incomplete on paging (beforeId) and folder/account semantics, which an agent needs to call it correctly.

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 0% and there are four parameters (limit, folder, beforeId, accountId), so the description carries the full burden. It says nothing about folder selection, result limits, beforeId-based paging, or account scoping, leaving every parameter semantically bare.

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 specific verb (list) and resource (messages in one mailbox folder) plus ordering, which distinguishes it from list_mailboxes and get_message. It does not explicitly differentiate from search_messages, so it falls short of 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?

Usage is implied by the scope phrase 'one mailbox folder, newest first', which suggests a browsing/fetch-recent flow rather than a query. There is no explicit when-to-use, when-not-to-use, or named alternative such as search_messages.

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