Mark or flag emails

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

Annotations already declare readOnly=false, idempotent=true, destructive=false and openWorld=true, so the safety profile is covered. The description adds essentially nothing beyond the action enum itself — it doesn't mention the same-folder constraint, rate/volume limits (200 ids), or that unflag reverses flag in an idempotent way. With annotations carrying the bar, this is a minimal contribution.

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 tight sentence with the action set front-loaded and no filler. It is appropriately sized for a simple state-toggle tool, though it spends its one clause restating what the action enum already shows.

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 4-param mutation with full schema coverage and no output schema, the description is adequate but thin. It omits any note that all ids must come from one folder and that folder defaults to inbox, details present in the schema but worth reinforcing in prose for a mutation tool.

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 the ids, action, folder and account semantics are fully documented in the schema itself. The description only mirrors the action values and adds no format or edge-case detail, which is the expected baseline when the schema does the heavy lifting.

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 states a specific verb set ('marks as read or unread, or flags/unflags') against a clear resource ('messages'), so an agent can tell it apart from move_emails or search_emails. It stops short of naming any sibling explicitly, which is the only thing separating it from a 5.

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?

Usage is implied by the action verbs, but there is no explicit guidance on when to use this versus move_emails, nor any stated prerequisites such as needing ids from a search within the same folder. The agent must infer the workflow.

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