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

Annotations only cover safety flags (not readOnly, not destructive, not openWorld), and the description adds substantial behavior beyond that: the return includes the new state and next snapshotId so no extra snapshot is needed, a changed window results in a no-op with the current state returned for retry, and a sent action is not proof of success. It also discloses the permission requirement.

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?

Front-loads the action, then sequences return behavior, error handling, the success caveat, and permissions. Every sentence carries actionable information with no padding.

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 still explains the return value (new state plus next snapshotId) and the failure mode (error carrying current state to retry from). Combined with the permission note, an agent has everything needed to call and interpret it correctly.

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 description coverage is 50% (deviceId and workSessionId are documented in the schema; elementId and snapshotId are not). The description implicitly explains snapshotId by tying it to the latest app_snapshot and elementId as an adjustable element, but adds no syntax or format detail, so it only partially compensates. Baseline 3 is appropriate.

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 ('Step a slider, stepper or other adjustable element ... up by one step') that immediately separates it from the sibling app_decrement. An agent knows exactly what operation and target this performs without opening the 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?

Provides clear operating context: it acts on the latest app_snapshot, consumes a snapshotId, and requires ui and process permission. It does not explicitly contrast with app_decrement or spell out when-not to use it, so it falls short of full when/alternatives guidance.

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