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Blender MCP Ultra

Blender MCP Ultra

by 3bdull4h2008
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Local

create_vertex_group

Add a named vertex group to a mesh object by specifying object and group name, enabling targeted vertex selection and weight assignments.

Instructions

Create a new vertex group on a mesh object.

Args: object_name: Target object. group_name: Name for the vertex group.

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": {
      "object_name": "<object_name>",
      "group_name": "<group_name>"
    },
    "name": "create_vertex_group"
  }
}

Input Schema

NameRequiredDescriptionDefault
group_nameYes
object_nameYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv3.0.0

TDQS

C2.7/5.0
Behavior2/5

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

No annotations are provided, so the description carries full responsibility for behavioral disclosure. It only says 'create a new vertex group' with no mention of side effects (e.g., overwriting an existing group), required object state, error conditions, or whether the operation affects the active object or a named one.

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

Conciseness4/5

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

The description is very brief and front-loaded, with no filler or redundant phrasing. Every word serves a purpose, but the under-specification limits the value of the conciseness.

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

Completeness2/5

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

For a tool with two simple string parameters and no output schema, the description covers the basics but omits important context an agent needs for correct invocation: whether the object must exist and be a mesh, what happens if the group already exists, and whether any mode or selection is required. The sibling assign_vertex_group suggests a workflow, but this tool's description does not place it in that workflow.

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

Parameters2/5

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

With schema description coverage at 0%, the description must compensate. It provides only terse labels—'Target object' and 'Name for the vertex group'—which add little beyond the schema titles 'Object Name' and 'Group Name'. No format, constraints, or relationships are explained.

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

Purpose4/5

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

The description states a specific verb ('Create') and resource ('a new vertex group on a mesh object'), clearly identifying the action and target. It implicitly distinguishes from the sibling assign_vertex_group by focusing on creation, but it does not explicitly name or contrast any sibling.

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 guidance on when to use this tool versus alternatives, such as assign_vertex_group, nor does it mention any prerequisites or exclusions. The only usage signal is the action itself, which is implied rather than stated.

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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