draw_arcCreate an arc in the most recent sketch by specifying center coordinates, start point, and sweep angle. Use it to add curved sketch geometry for CAD profiles and models.
Draw an arc in the most recent sketch (center + start point + sweep angle)
| Name | Required | Description | Default |
|---|---|---|---|
| start_x | Yes | ||
| start_y | Yes | ||
| start_z | No | ||
| center_x | Yes | ||
| center_y | Yes | ||
| center_z | No | ||
| sweep_angle | Yes | Sweep angle in degrees (positive = CCW) |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations indicate this is a non-readOnly, non-idempotent, non-destructive operation, which the description doesn't contradict. However, it adds little behavioral context beyond the basic action—no mention of effects on the sketch, error conditions, or visual feedback. With annotations covering safety, the description provides minimal additional value.
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 waste—every word contributes to defining the tool's purpose. It's appropriately sized for a straightforward geometric operation, avoiding redundancy or fluff.
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?
Given the complexity (7 parameters, low schema coverage, no output schema) and annotations, the description is incomplete. It lacks details on parameter usage, expected outcomes, or integration with the sketching workflow. For a CAD tool with multiple numeric inputs, more context is needed to guide effective use.
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 low (14%), with only sweep_angle documented. The description mentions parameters generically ('center + start point + sweep angle') but adds no meaning beyond naming them—no units, coordinate system, or geometric relationships. It fails to compensate for the poor schema coverage, leaving most parameters unclear.
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 clearly states the specific action ('Draw an arc') and the resource ('in the most recent sketch'), with precise geometric parameters (center + start point + sweep angle). It distinguishes from sibling tools like draw_circle, draw_line, and draw_rectangle by specifying arc creation rather than other sketch primitives.
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?
The description provides minimal guidance, only implying usage for arc drawing in sketches. It lacks explicit when-to-use criteria, prerequisites (e.g., requires an active sketch), or alternatives (e.g., using draw_spline for curves). No exclusions or comparisons to siblings are mentioned.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.