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

Annotations only say readOnly=false and destructive=false; the description goes much further by naming the terminal states (ready, idle), the idle reasons (verify_failed, download_failed), the no_update failure, the guarantee that nothing is applied, that it is simulated, and that each state change lands in device_log.

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 tight sentences: action first, then outcome states, then failure modes. The parentheticals carry real information (state names, the never-applied guarantee) rather than filler.

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?

With no output schema, the description compensates well by enumerating return states and failure reasons. The only gap is the absence of an explicit next-step pointer to apply_update, which an agent must infer from 'never applied'.

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?

Only one parameter, and the schema already documents it at 100% coverage ('Session from open_app'). The description adds no extra meaning about how the session is used or whether it must come from a specific app state, so this sits at the baseline.

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 and resource (ask the update source for a newer release) plus the exact operations performed (signature and hash check, download). The clause 'the release is never applied' cleanly separates it from the apply_update sibling.

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?

Makes clear this is the pre-flight/check-and-stage step and that failure is expected when nothing newer exists (no_update). It does not explicitly name apply_update as the follow-up call, so the sequencing is implied rather than stated.

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