nex_mail_message_list

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

Beyond the single readOnlyHint=false annotation, the description discloses the poll interval (every 10 seconds), the terminal failure mode (MAIL_MESSAGE_TIMEOUT on a confirmed empty wait), pagination (10 per page), and a rate limit of 5 read calls per 3 seconds. What it does not disclose is what "sync" mutates locally or what permissions the mailbox id requires.

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?

Front-loads the core action and paging, then walks through waitSeconds, receivedAfter, onlyNew in a logical order; no filler sentences. The telegraphic clause stacking ("Still match recipient and site") costs some readability but nothing is redundant.

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 6-parameter tool with zero schema descriptions and no output schema, the definition covers the behavioral essentials: sync timing, pagination, timeout error, rate limit, and the filtering traps. Returning field shape is not explained, but the function is a list, so that gap is minor.

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%, so the description must carry the load, and it does: waitSeconds semantics, receivedAfter's timezone requirement and filtering behavior, onlyNew's baseline definition, and the keyword rule (codes come from the full keyword, never keywordDisplay). Only `page` is left implied by "10 per page" rather than described.

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 compound verb ("Sync and list email") scoped to a local mailbox id, and names the paging size. An agent knows this retrieves mail messages rather than domains, plans, or records. It does not name the natural sibling nex_mail_message_detail, so the distinction from detail-fetching is left implicit.

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 concrete selection rules: waitSeconds 0 for a single sync, 180 to wait for verification mail, and onlyNew "for use after a resend". These are real when-to-use conditions rather than platitudes. It stops short of explicitly excluding or pointing to nex_mail_message_detail for reading a single message body.

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