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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so safety is covered. The description adds real context on top: the id is an IMAP uid 'scoped to the folder it was found in — not the email's Message-ID header,' which is a meaningful behavioral caveat. It omits auth requirements and rate limits.

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 tightly written sentences with no redundancy: the purpose is stated first and the parameter caveat second. Every clause 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 read-only, two-parameter tool with no output schema, the description covers the return value ('full text of one email'), how to obtain the uid, and the folder scoping. Minor gaps like auth requirements remain, but nothing needed to call it correctly is missing.

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%, setting a baseline of 3, but the description goes further by explaining that message_id is an IMAP uid from the listed tools and is folder-scoped, not the Message-ID header. That is semantic value beyond the schema text.

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: 'Read the full text of one email ... by its uid.' The 'one email by uid' framing implicitly distinguishes it from the sibling search/list tools, but it never explicitly names them as the alternative.

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?

The description points to email_search and email_list_recent as the sources of the uid, which implies when this tool is used. However, it gives no explicit when-to-use vs when-not guidance or conditions that would route an agent here over a sibling.

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