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

Beyond annotations, describes sorting order and multi-folder scope. Does not mention behavior for limit parameter or when both IDs are provided, which are minor gaps.

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?

Concise two-sentence description with no unnecessary words. Each sentence conveys essential information.

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?

Covers the core functionality well given the existence of an output schema. Missing details on limit parameter and edge cases (e.g., missing ID) are minor but notable gaps.

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?

With 0% schema coverage, description adds meaning for message_id and header_message_id by clarifying their sources. However, limit parameter is not explained, and behavior when both IDs are given is omitted.

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 it retrieves all messages in a single thread, sorted oldest first, across folders and accounts. Differentiates from mail_search by specifying how to reference 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?

Provides explicit guidance on how to provide input (message_id from mail_search or RFC header_message_id). Indicates use case for reconstructing discussions spanning folders, but lacks explicit when-not-to-use instructions.

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