Read one Gmail message

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

Annotations already declare readOnly, openWorld and idempotent, so the safety profile is well covered. The description adds a small practical constraint ('always pass both') and the mailbox-search provenance, but does not disclose additional behavioral details such as return format or possible errors. This meets but does not exceed the bar.

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?

Two short sentences, no padding, and the most important constraint ('Always preserve both...') is placed after the core action. Every sentence earns its place.

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 simple, read-only two-parameter tool with strong annotations and a clear sibling context, the description is nearly complete. It could have stated what the read operation actually returns, but the low complexity and explicitly safe behavior make this a minor gap.

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 schema already fully documents both parameters. The description essentially reiterates the schema's assertions ('source mailbox alias', 'message ID returned by a search') without adding new detail, so a baseline of 3 is appropriate.

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 and resource ('Read a Gmail message') and immediately scopes it to 'returned by a mailbox search,' which distinguishes it from the mailbox-management and search sibling tools. This is clear, direct, and actionable.

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 clearly indicates that the tool operates on search results and requires both the source mailbox alias and message ID. It does not explicitly mention alternatives or say when not to use it, but the context and sibling list make the usage scenario clear.

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