Resize an Electron app's viewport for a test session by specifying session ID, width, and height, so visual and layout checks run at target dimensions.
Set the viewport size
| Name | Required | Description | Default |
|---|---|---|---|
| width | Yes | ||
| height | Yes | ||
| sessionId | Yes |
Changes observed during successful MCP inspections.
v1.0.3Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden of behavioral disclosure and fails to do so. It does not say whether the change is session-scoped or persistent, whether it affects screenshots, or what happens on invalid dimensions. It at least does not contradict anything.
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?
A single four-word sentence is short but is under-specification rather than concision; there is nothing to front-load because there is no substance.
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 three-required-parameter mutation tool with no annotations, no output schema, and no parameter documentation, the description is wholly inadequate and leaves an agent unable to call 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?
The schema has 0% description coverage for all three required parameters (sessionId, width, height), and the description supplies no meaning, units, ranges, or format guidance. The bare schema gives types but nothing about pixel units or session identity semantics.
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 'Set the viewport size' is essentially a restatement of the tool name set_viewport_size, which the rubric classifies as tautology. It conveys the verb and resource but offers zero differentiation from siblings such as get_viewport_size or set_device_metrics.
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?
There is no guidance on when to use this tool versus alternatives like set_device_metrics, emulate_network_conditions, or get_viewport_size. An agent must infer usage entirely from the name.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.