update_message

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

With no annotations, the description carries the behavioral disclosure burden. It does add useful context: 'patches in-place,' the parent_folder_id caveat, and 'Returns the trimmed updated message.' Still, it does not explain what null/default values do to existing fields, whether categories are replaced or appended, or any permission/reversibility implications for this 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?

Three short sentences: the purpose is front-loaded, the routing caveat is compact, and the return behavior is stated last. There is minimal filler, and the structure makes the key information easy to scan.

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?

The description is adequate for the happy path but not complete for this tool's complexity. It omits clear explanations of mailbox and include_raw, does not distinguish from read/flag convenience siblings, and 'trimmed updated message' is vague about the response shape. Given no output schema and no annotations, these are notable gaps.

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 coverage is 0%, so the description must compensate. It only maps four high-level fields (read state, flag, importance, categories) and adds no semantics for mailbox, include_raw, message_id, or how parent_folder_id behaves beyond 'works but is not the primary path.' The schema titles and enums do some work, but the description does not add enough meaning for the full 8-parameter surface.

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 opens with a specific verb and resource: 'Patch a message's read state / flag / importance / categories.' It also explicitly distinguishes itself from move_message, which is the main sibling that could be confused for this tool.

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?

It gives explicit routing guidance for folder movement: 'prefer move_message' and clarifies that parent_folder_id works but is not the primary path. However, it does not guide the agent toward or away from the specialized siblings mark_read, mark_unread, flag_message, or unflag_message, which overlap directly with this tool's stated purpose.

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