Add a horizontal or vertical guide line at a chosen percentage position to align and structure generative art layouts.
Add a custom horizontal or vertical guide line at a specific position.
| Name | Required | Description | Default |
|---|---|---|---|
| position | No | Position as percentage 0–100 (default: 50). | |
| guideColor | No | Guide color. | |
| orientation | Yes | Guide orientation. |
Changes observed during successful MCP inspections.
v0.5.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full behavioral burden. It only says a guide is added at a position, without disclosing whether the change is undoable, requires specific permissions, affects the active layer, or how custom guides differ from other guides.
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 a single, front-loaded sentence with zero wasted words. Its brevity is appropriate for a simple add operation, even though it leaves other important information unstated.
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 low-complexity tool with complete schema parameter descriptions and no output schema, the description is minimally sufficient to call the tool. However, with no annotations and many overlapping guide-related siblings, it should clarify the custom-guide distinction and mutation behavior.
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 100%, so the schema already explains orientation, position, and guideColor. The description reinforces orientation and position but adds no syntax, defaults, or coordinate-system context beyond what the schema provides.
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 ('Add') and resource ('custom horizontal or vertical guide line') with orientation and position detail. It does not, however, distinguish this from the sibling tool design_add_guide, leaving ambiguity about when this 'custom' variant is preferred.
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 the many sibling guide tools such as design_add_guide, design_toggle_guides, or design_clear_guides. The agent must infer usage from the tool name alone.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.