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

Annotations already declare readOnlyHint=false, idempotentHint=true, destructiveHint=false. The description adds the key side effect 'marks the email as read', which is crucial. It also enumerates what content is returned. It doesn't mention authentication or rate limits, but those are not critical for a simple read-like operation. No contradiction with annotations.

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 two short sentences. The first states the purpose and content coverage, the second reveals the side effect. It is front-loaded and contains no filler. Every word adds value.

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?

With only one parameter, no output schema, and low complexity, the description fully captures what the tool does, what it returns, and its side effect. Annotations cover safety profile. Nothing essential 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?

The schema covers 100% of parameters (only 'id' with description 'Email ID (UUID)'). The description merely repeats the parameter name and doesn't add extra meaning, such as where the ID comes from or format nuances. Baseline 3 is appropriate since the schema already documents it.

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 clearly states the action (read full content), the resource (single email), and the scope (by ID, including headers, body, attachments metadata). It distinguishes from sibling tools like list_emails which likely provide summary metadata without full content.

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 implies when to use this tool (when full content of a specific email is needed). It doesn't explicitly mention alternatives or exclusions, but the context with siblings like 'list_emails' and 'archive_email' makes the usage obvious. A brief 'use this instead of list_emails when you need full content' would be a 5.

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