phone_open_app

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

Annotations already declare the write/destructive/open-world profile, so safety is covered. The description adds genuinely new behavior: it consumes the observation and requires re-observing afterward, which the annotations do not convey.

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?

Two compact clauses with the critical constraint (real packageName, latest observationId) and the post-effect (re-observe) front-loaded. No wasted text.

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?

Covers the prerequisites and side effects an agent needs to call it correctly. Minor gap: no statement of what the call returns or how success/failure is signaled, though no output schema exists to compensate elsewhere.

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 must carry meaning, and it does: packageName must be the real one returned by phone_apps, and observationId must be the latest. Both required parameters gain operational meaning beyond their types/patterns.

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 (open) and resource (app), and distinguishes itself from siblings by naming phone_apps as the source of the packageName. An agent can tell it apart from phone_action/phone_observe without opening any schema.

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?

Explicitly tells the agent it must use the real packageName obtained from phone_apps and pass the latest observationId, establishing prerequisites and routing to the right sibling. No explicit 'when-not-to-use', but the preconditions are clearly stated.

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