Flag an email

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

Annotations already convey readOnlyHint=false, destructiveHint=false, idempotentHint=true, and openWorldHint=true. The description adds no behavioral context beyond those annotations; it restates the seen/flagged actions without disclosing additional traits such as authorization needs or side effects, so it meets the baseline but does not exceed it.

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?

A single, front-loaded sentence communicates the complete purpose with no filler or redundancy. Every word contributes to understanding the tool's scope.

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 annotations, full parameter schemas, and an output schema, the concise description is sufficient for an agent to select and invoke the tool correctly. The only slight tension is the title, but the description resolves it, so 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?

Schema description coverage is 100%, so every parameter (uid, seen, folder, flagged) already has a clear schema description. The tool description adds no additional parameter semantics beyond what the schema provides, matching the baseline for full schema coverage.

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 uses a specific verb ('mark') and resource ('a message') and enumerates the exact operations: read/unread and flag/unflag. Although the title 'Flag an email' is narrower, the description clarifies the full scope and distinguishes this from sibling tools like read_email, move_email, and delete_email.

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 context is clear: use this tool when a message's seen or flagged state needs to be changed. However, the description does not explicitly state alternatives or exclusion conditions, such as 'use read_email if you only need to view the message,' so usage guidance is implied rather than stated.

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