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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds nothing behavioral on top: not what is counted (messages vs threads), not whether filters intersect or union, not any workspace/auth scoping or rate-limit context.

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?

A single short sentence with the core metric front-loaded and no filler. It is a fragment rather than a full sentence, but nothing is wasted.

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 two-optional-parameter counter with full annotation coverage and no output schema, the definition is minimally viable. It still leaves the agent guessing about filter interaction semantics and the counting unit, which is the main gap.

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 carries the full burden for the two filters. It gestures at both (mailboxes, campaign) but never explains the expected format for mailboxes, the campaignId meaning, or what happens when both filters are supplied — the most important ambiguity for this tool.

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 names a concrete resource and metric (unread email count) with an optional scoping dimension, so the agent knows exactly what is produced. It stops short of distinguishing itself from nearby siblings like list_emails or get_workspace_analytics, which also surface email/count information.

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?

'optionally for some mailboxes or one campaign' is a parameter hint, not usage guidance. There is no statement of when to reach for this instead of list_emails, get_mailbox, or get_workspace_analytics, and no note about the workspace/user scope the count applies to.

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