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

Annotations only declare readOnlyHint=false and destructiveHint=false; the description adds real value beyond them by describing the state transition, the specific failure mode (not_installed), and that the action is recorded in device_log as simulated. What is missing is any indication of return payload or whether prior app state is preserved.

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 compact clauses, front-loaded with the action and effect, then failure mode, then logging. Every clause carries information, though the sentence is slightly telegraphic.

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, non-destructive action with no output schema, the description covers the observable effect, the failure case, and the audit trail. The main residual gap is what the tool returns on success and whether an existing current_app is affected.

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. The description reinforces that 'id' must refer to an installed app and that 'session' comes from a prior flow, but adds no format or constraint detail beyond the schema, so the baseline of 3 applies.

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 gives a concrete verb and resource ('Open an installed app (tap its icon on the home screen)') and states the resulting state change ('becomes current_app and comes to the front'), which is more than a restatement of the name. It stops short of naming how it differs from the sibling open_app/resume_app, so an agent must infer the boundary.

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?

Usage is implied by the phrase 'installed app' and by the home-screen-tap framing, which suggests it is for apps already installed rather than installing them. There is no explicit when-to-use or when-not-to-use guidance relative to open_app, resume_app, or install_app, all of which sit in the same family.

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