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

Annotations only supply destructiveHint=true and idempotentHint=false; the description adds the crucial nuance that this is a soft, recoverable delete (Trash), that already-trashed messages are rejected, and that batching is required. These are non-obvious behavioral traits an agent could not infer from the annotations alone.

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?

Four sentences, front-loaded with the core action and scope, each carrying distinct information (recoverability, same-folder rule, Trash refusal, batching). The permanence sentence is a bit long but justifies itself by preventing a dangerous assumption.

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 no output schema, the description still covers the essential behavior, refusal case, and batch expectation. It omits what happens on partial failure (e.g., UIDs spanning folders) and whether per-message results are returned, which would matter for a 500-item batch call.

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 the baseline is 3, but the description adds a real constraint beyond the schema: every UID must be in the same folder, and all UIDs should be passed in one call rather than one per message. It does not, however, relate the mailbox parameter to that same-folder constraint.

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 states a specific verb+resource ("Move messages to the Trash folder") and immediately distinguishes it from permanent deletion, which it explicitly says it does not perform. An agent can separate this from siblings like archive_email, move_email, or delete_folder without opening any 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 usage context (clicking Delete in Outlook/webmail) and explicit exclusions: all UIDs must share one folder, and messages already in Trash are refused. It references a "separate, explicitly named operation" for permanent deletion without naming the sibling tool, so routing is implied rather than spelled out.

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