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

The description adds critical functional context beyond the annotations, detailing that the output includes the body (text/html) and attachment list, and specifically noting that attachment *content* is omitted.

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 highly concise, packing the core functionality, input requirements, and default operational safety into a single, highly dense sentence.

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 strong safety guarantees provided by the annotations (readOnlyHint: true), the description provides all the necessary behavioral and functional details for an agent to use the tool accurately.

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?

While the schema defines the parameters, the description provides the crucial semantics for the `mark_read` parameter, explaining its default state and how it controls the mutation behavior of the read status.

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 explicitly states the tool retrieves one specific email message, identifying the inputs as either an ID or a UUID, which is highly specific and easy to parse.

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 provides clear usage logic regarding the `mark_read` parameter, stating that the default behavior is not to mark it read unless explicitly told otherwise. This guides the agent's implementation context.

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