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

The annotation readOnlyHint=true and the verb 'get' make the read-only nature clear. The description also discloses that it returns failure reasons when applicable, providing transparency about the kind of data returned without suggesting side effects.

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 a single focused sentence that front-loads the purpose and lists the returned fields without unnecessary detail. It is concise and well structured.

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 no output schema present, the description compensates by enumerating the key output fields (subject, recipients, time sent, time received, and failure reason). This gives an agent sufficient context to know what to expect from the call.

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 already fully describes the single id parameter as the identifier of the email history record. The description merely repeats 'by id' and adds no additional semantic detail beyond the schema, so the baseline score applies.

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 (get one sent email's history record), the lookup method (by id), and the specific fields returned (subject, recipients, time sent, time received, failure reason). This is distinct from list_emails, which lists emails rather than fetching a single history record.

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 usage when a single email history record is needed by id, but it does not explicitly contrast with list_emails or other email-related tools. Guidance is present but only implicit.

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