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

Annotations only supply destructiveHint=false, so the description carries real weight here and delivers: it discloses the permission requirement (gmail.modify), a migration caveat (pre-feature accounts need reconnect), and the restore target (prior labels). It stops short of describing failure modes or whether already-untrashed messages error.

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?

Three short sentences, each front-loaded with a distinct fact: what it does, when to pass account, what permissions are needed. No filler or repetition.

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-parameter tool with no output schema, the description covers the operation, the optional-parameter condition and the auth requirement. Only minor gaps remain (behavior on messages not in Trash, return shape), which are low-impact here.

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%, so the schema already documents both parameters. The description's account guidance about multiple connected accounts largely restates the schema's own text, adding little new semantics; baseline 3 applies.

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 (restore) + resource (Gmail message from Trash) + scope ('ONE') + destination ('back to its prior labels'). Together with the sibling name trash_message, an agent immediately knows this is the inverse operation and that it operates on single messages.

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 clear conditional guidance for the optional parameter ('Pass account when more than one Gmail account is connected') and states the auth prerequisite (gmail.modify, plus a reconnect hint for older accounts). It doesn't explicitly contrast with trash_message or modify_message_labels, but the restore-from-Trash context makes the use case unambiguous.

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