update-mail-rule

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

Annotations mark destructiveHint: true and readOnlyHint: false, which the description aligns with ('change', 'save'). The description adds meaningful behavior beyond annotations: it clarifies PATCH semantics ('send only the properties to change'), and notes that only writable properties are affected. No contradiction. The confirm-gate behavior is documented in the schema, not the description, but that's acceptable given the annotations.

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 two sentences plus a well-placed tip. The main purpose is stated first, followed by practical guidance. The tip is a bit long but packed with useful info (how to get folder ID, partial updates, example). No fluff or repetition; it's efficiently organized.

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 large, detailed schema and no output schema, the description covers the essentials: what it does, how to get the folder ID, partial-update behavior, and a common scenario. It doesn't mention the confirm gate or return fidelity (excludeResponse, includeHeaders), but those are schema-level. For an update tool with a rich schema, this is reasonably complete.

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 83% (high), so the schema already explains most parameters. The description adds value by explaining how to use the body: 'Send only the properties to change' and gives a common-use example ({ isEnabled: false }). It also reinforces the need for mailFolderId and messageRuleId via the tip. This goes beyond the schema's basic property descriptions.

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 ('change writable properties'), resource ('messageRule object'), and action ('save the changes'). It clearly distinguishes from create-mail-rule (existing rule) and delete-mail-rule, and the sibling list confirms these alternatives exist. The agent knows exactly what this tool does and when to pick it.

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 gives explicit usage guidance: 'Updates an existing message rule', 'Use the Inbox folder ID (get it from list-mail-folders) for inbox rules', 'Send only the properties to change'. It also provides a concrete example (disabling a rule). It does not explicitly name alternatives (e.g., create-mail-rule) but implies the distinction via 'existing', which is sufficient for most agents.

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