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

Beyond the destructiveHint annotation, the description discloses recoverability, same-folder requirement, refusal on already-trashed messages, and single-operation batching. This gives a solid behavioral picture, though some edge-case details (e.g., error behavior) are absent, so it falls short of a perfect 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 description is concise yet comprehensive, with each sentence serving a purpose—behavior, constraint, batch instruction, and parameter clarification. No fluff or redundancy; it is well-structured for easy parsing.

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?

Given the absence of an output schema, the description fully covers what the tool does, its constraints, and how to invoke it correctly. It answers likely questions (what happens to messages, what if already in trash, how many UIDs) without needing extra information.

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?

The schema covers both parameters with descriptive comments (100% coverage), and the description adds meaningful context about batching and the one-element array for a single message. Since the schema already provides high coverage, the extra description elevates it above baseline but not to the top tier.

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?

Clearly states the tool moves messages to the Trash folder, with an explicit analogy to clicking Delete in Outlook. It also distinguishes itself from permanent deletion, making its purpose unambiguous relative to siblings like move_email or delete_folder.

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?

Provides explicit usage and prohibition guidance: refuses to run on messages already in Trash (because permanent deletion is a separate operation) and instructs to pass all UIDs in one call. This leaves no doubt about when and how to use the tool.

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