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Fusion360 Live MCP

Fusion360 Live MCP

by tbrito88
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Hybrid

Draw Arc

draw_arc

Create an arc in the active sketch by defining its center, start point, and sweep angle. Use centimeter coordinates and degree angles to add curved sketch geometry.

Instructions

Draw an arc in the most recent sketch (center + start point + sweep angle) Unless a parameter says otherwise, lengths and coordinates are in cm (not mm) and angles in degrees.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "center_x": "<center_x>",
      "center_y": "<center_y>",
      "start_x": "<start_x>",
      "start_y": "<start_y>",
      "sweep_angle": "<sweep_angle>"
    },
    "name": "draw_arc"
  }
}

Input Schema

NameRequiredDescriptionDefault
start_xYes
start_yYes
start_zNo
center_xYes
center_yYes
center_zNo
sweep_angleYesSweep angle in degrees (positive = CCW)

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

A3.5/5.0
Behavior3/5

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

Annotations already declare readOnlyHint=false, idempotentHint=false, and destructiveHint=false, so the mutation profile is known. The description adds useful unit context (cm, degrees) and sketch scope, but does not disclose whether an active sketch is required, what happens if none exists, or other behavioral constraints.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two efficient sentences with no wasted text. The core action and scope are front-loaded, and the unit caveat follows immediately.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a mutation tool with no output schema and low parameter coverage, the description covers the basic action, sketch target, and units. However, it omits prerequisites such as requiring an active sketch and does not clarify the working plane or coordinate system, leaving notable gaps for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is only 14%, so the description must compensate. It adds critical unit semantics for lengths and angles, but does not explain coordinate order, z-coordinate defaults, or the meaning of optional center_z/start_z beyond what parameter names imply.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource: 'Draw an arc in the most recent sketch.' It also names the geometric definition (center + start point + sweep angle), which distinguishes it from sibling draw_* tools like draw_circle and draw_line.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives no explicit when-to-use, when-not-to-use, or alternatives guidance. It implies an active sketch is needed by saying 'in the most recent sketch,' but it does not state that prerequisite or route the agent to sibling tools.

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

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