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

Beyond readOnlyHint=true and openWorldHint=false, it discloses the default page size (20), default ordering, the output fields per entry, and the important caveat that a UID is only unique within the folder it was listed from. That UID-scoping warning is genuine behavioral context that neither annotations nor schema carry.

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?

Four tight sentences, front-loaded with the core behavior and ending on the gotcha. The list of per-entry fields slightly duplicates the output schema, a minor redundancy.

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?

With an output schema present, return values need not be explained; the description still covers ordering, paging and UID scoping adequately. Only the absence of guidance against sibling tools leaves a small hole.

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 coverage is 100%, so every parameter is already documented, and the description mostly restates it ('order=oldest_first', 'offset pages further'). Baseline 3 applies when the schema does the heavy lifting.

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?

Specific verb+resource with scope: 'List the emails in one folder, newest first by default, 20 at a time.' An agent can distinguish this from search_emails or read_email by the 'list one folder' framing, though no sibling is named explicitly.

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 paging and ordering context implies when this is the right tool (enumerate a folder) but never states when to prefer search_emails or read_email instead, nor any prerequisites such as having a valid mailbox name.

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