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

Annotations already declare readOnlyHint=true, destructiveHint=false and a closed-world scope, so 'Read-only' is largely redundant. The description does add value by disclosing the shape of the payload (aliases, entity mappings, capture counts, sender→label table), but says nothing about ordering, paging, or how stale the learned table might be.

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 dense sentences with the resource and payload front-loaded and the usage rule trailing. No filler or restated title text.

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?

The return payload is described well enough to substitute for a missing output schema, and the safety profile is covered by annotations. However, for a tool with two entirely undocumented parameters, the definition leaves an agent unsure how to filter or whether archived labels appear by default.

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?

Both parameters (`q` and `include_archived`) have 0% schema description coverage, and the description never mentions them. An agent must guess whether `q` searches label names, aliases, or sender strings, and whether archived labels are excluded by default.

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 specific resource (the caller's client labels) and enumerates what it returns: aliases, mapped cabinet entities, capture counts, and the learned sender→label table. It distinguishes itself from write-ish siblings by declaring 'Read-only' and by framing itself as the lookup step before assigning, though it never names intake_manage_labels or mail_list_labels directly.

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?

'Use before assigning, to pick an existing label instead of creating a near-duplicate' gives a concrete when-to-use condition and implicitly steers agents away from creating labels. It stops short of explicitly naming which sibling to use for creation or how archived labels affect the decision.

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