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

With no annotations, the description carries the full behavioral burden and does so thoroughly: it discloses continuous-touch semantics, first/last point roles, no densification, HID preference with MotionEvent fallback, and physical-pixel coordinate space. This goes well beyond what the schema alone reveals.

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 densely informative with no filler. Front-loaded purpose is followed by parameter semantics, behavioral delivery details, coordinate space, and cross-platform pointer, with every sentence earning its place.

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 gesture-input tool with no output schema, the description plus schema fully equips an agent to call it correctly: purpose, usage boundaries, input semantics, delivery mechanism, coordinate system, and cross-platform alternative are all present. Nothing critical 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 the baseline is 3. The description adds meaningful semantics beyond the schema for `points` — ordered waypoints, touch-down/lift roles, and 'as given' fidelity — and clarifies physical-pixel coordinate meaning. It does not elaborate on `durationMs`, but the schema already documents its default and range.

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: 'Replay a freeform stroke as ONE continuous touch'. It explicitly contrasts with a sibling by mentioning 'any gesture a straight device_swipe cannot express', so an agent can distinguish it 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?

It names concrete use cases (curves, arcs, signatures, unlock patterns) and points to the alternative device_swipe for straight gestures, while also naming the iOS counterpart. It further advises the agent to pass enough points because waypoints are not densified, which is practical usage guidance.

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