message_update

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

With no annotations, the description must carry the behavioral burden. It mentions the auth requirement and the operation scope, but does not disclose whether flags/labels are replaced or merged, what happens when the message does not exist, or any error/return behavior. This is a reasonable but not deep disclosure for a mutation tool.

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 verb and resource, immediately conveys the scope, and includes an essential prerequisite without any filler. Every word contributes to understanding.

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 simple update tool with no output schema, the description covers the essential context: what it does, its domain (IMAP alias), and an authentication requirement. It does not describe expected return values or error scenarios, but these are less critical given the straightforward nature of the operation. It is almost complete for its complexity.

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 has 100% parameter description coverage, so the schema carries the semantic details. The description's mention of 'flags/labels/folder move' loosely maps to parameters, but adds no additional meaning beyond what the schema already states. The baseline of 3 is appropriate.

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: 'Update a message' with specific sub-operations (flags/labels/folder move) and the scope ('for an alias (IMAP)'). This distinguishes it from sibling tools like message_create, message_get, and message_delete.

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 provides clear context on when to use the tool (updating an existing message) and a prerequisite ('Requires alias credentials'). It does not explicitly name alternatives or exclusions, but the specific sub-operations make the intended use obvious relative to siblings.

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