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

Annotations already declare destructiveHint=true and idempotentHint=true, and the description goes well beyond them by disclosing that no messages are deleted and that effects differ by provider (Gmail label removed from every message, Outlook category removed from the list, messages keep the name). The final sentence about imap is worded so ambiguously ('deletes only a folder holding no mail and no folder') that the critical edge case is hard to parse, which keeps this from a 5.

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?

The action is front-loaded and the 'No message is deleted' clause earns its place, but the provider sentence is dense and the trailing imap sentence is convoluted enough that a reader must re-parse it. That sentence arguably fails to earn its place in its current form.

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?

With annotations covering the destructive/idempotent profile and an output schema present, the description supplies the remaining piece an agent needs: what actually happens to messages under each provider. The only gap is the muddled imap behavior, which leaves one provider's outcome uncertain.

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 coverage is 100%, so both parameters are already documented; the description only reinforces that id comes from labels_list. It adds no format, constraint, or failure-mode detail beyond the schema, so the baseline of 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?

States a specific verb and resource ('Delete one label') plus the identifier source ('by its id from labels_list'), which separates it cleanly from labels_create and labels_update. An agent knows exactly what the tool does without opening the schema.

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?

It gives clear operational context: the id must come from labels_list, and it explains the message-level consequences of deleting. It does not explicitly say when to prefer labels_update over delete, nor does it warn to confirm before invoking a destructive call, so no true exclusions are present.

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