Star or unstar a message

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

Annotations already declare it as a non-read-only, idempotent, non-destructive write with open-world reach, so the safety profile is covered. The description adds valuable context beyond that: the star state propagates across the phone and linked devices, and the tool returns the affected message.

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, front-loaded sentence with no filler, plus a brief note on the return value. Every clause earns its place.

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 two-parameter tool with full schema coverage and annotations covering the safety profile, the description is nearly complete. It even notes the return value in absence of an output schema, though it omits error or failure behavior.

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 100%, giving a baseline of 3. The description goes one step further by defining the semantic effect of the `starred` boolean (false = unstar), which the schema's terse 'Default true.' does not make explicit.

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?

States a specific verb (star/unstar) and resource (a message), and explains the dual behavior via the `starred: false` switch. It is clearly distinguishable from siblings like react_to_message or pin_chat, which are separate operations on the same domain.

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?

Tells the agent how to trigger the inverse operation (unstar with `starred: false`), which implies the usage. However, it gives no explicit when-to-use guidance versus alternatives (e.g., react_to_message, pin_chat) and no exclusions or prerequisites.

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