List Gmail accounts

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

Annotations already cover the safety profile (readOnlyHint, openWorldHint, idempotentHint, destructiveHint=false), so the bar is lower. The description adds genuine behavioral context beyond that: accounts may exist yet be unusable, and this tool reports that state. It is consistent with annotations — listing is read-only and idempotent.

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?

Exactly two sentences: the first delivers the core purpose, the second front-loads the usage trigger. No filler, no repetition of schema or annotation content, and every sentence earns its place.

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 tool (one optional param, no required params, no output schema) with annotations covering safety, the description covers purpose and usage triggers well. The only minor gap is that the return format is not described and there is no output schema to fill it, but the shape of a discovery list is largely predictable.

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 100%: the single "probe" parameter is fully documented in the schema (boolean, contacts Gmail, slower, detects revoked tokens, defaults false). The description only hints at this via "whether it is usable," so the schema does the heavy lifting — baseline 3 is appropriate.

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?

"List every configured Gmail account and whether it is usable" names a specific verb (list), resource (configured Gmail accounts), and added scope (usability status). It is unambiguous against the sibling list_labels — that tool lists labels, not accounts — so an agent can tell them apart without inspecting schemas.

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?

"Call this first when you do not know which accounts exist, or when another tool reports an unknown account" gives explicit, actionable trigger conditions. For a discovery tool with no genuine sibling alternative, the absence of a when-not clause is not a real gap.

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