update_user_preferences

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

Beyond the annotations, the description reveals important behavioral details: the etag-based optimistic concurrency requirement and the 412 stale response. It also shows the endpoint and payload shape. There is no contradiction with 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 three short, information-dense sentences. It front-loads the purpose, then gives the precondition/error behavior, then the payload format. No filler or redundant restatement.

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 one-parameter update tool with no output schema, the description covers the essential call contract: what to update, the required etag, the stale-error behavior, and the payload format. It does not describe the response, but that is a minor gap given the tool's simplicity.

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 carries the burden. It explains user_preferences_json as a full/partial prefs object including etag and shows the enclosing POST body shape, which is enough for an agent to construct the argument.

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: 'Update Calendar user preferences.' It also clearly distinguishes the update action from the getter sibling get_user_preferences and adds the critical prerequisite of using an etag from that getter.

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 explicitly states when to call the tool: only with an etag from get_user_preferences, and notes the 412 failure on a stale etag. It does not explicitly list when-not-to-use alternatives, but no direct update competitor exists among the sibling tools.

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