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

Beyond the annotations, the description discloses important non-obvious behavior: the clock stays fixed and does not tick, null restores real time, and invalid input fails with bad_time. This is exactly the behavioral context an agent needs before invoking the tool. The annotations confirm it is a non-read-only mutation, which is consistent with setting the clock.

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 concise sentences, front-loading the core action, then explaining the simulation purpose and fixed-clock behavior, and finally the failure mode. Every sentence carries useful information without repetition.

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 two-parameter tool with full schema coverage and annotations, the description covers purpose, reset behavior, non-ticking semantics, and error behavior. Nothing essential for correct invocation is missing.

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%, so both parameters are already documented in the schema, including the null behavior for 'at' and 'session' coming from open_app. The description adds a concrete timestamp example and reinforces the null reset behavior, but does not add substantial parameter meaning beyond the schema.

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 and resource: setting the phone's clock to a given time. It also explains the practical purpose, making scheduled apps render as they would at that time. It is clear, though it does not explicitly distinguish itself from sibling tools such as set_device.

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 a clear usage context: use it to simulate scheduled app visibility at a future time. It also explains how to return to real time by passing null. It does not name explicit exclusions or alternative tools, which keeps it just short of the top score.

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