BlenderMCP

create_primitive

Add basic 3D shapes like cubes, spheres, and cylinders to Blender scenes for modeling and scene construction.

Instructions

Create a primitive mesh object.

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": {
      "primitive": "<primitive>"
    },
    "name": "create_primitive"
  }
}

Input Schema

Name	Required	Description	Default
`primitive`	Yes
`name`	No
`size`	No
`location`	No
`rotation`	No
`scale`	No

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedJan 21, 2026

TDQS

C2.8/5.0

Behavior2/5

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

No annotations are provided, so the description carries full burden for behavioral disclosure. While 'Create' implies a write operation, the description doesn't specify what happens after creation (e.g., whether the object becomes selected, appears in viewport, requires scene context), nor does it mention permissions, error conditions, or rate limits. This leaves significant behavioral gaps for a creation tool.

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?

The description is perfectly concise at 5 words, front-loading the essential action and object type with zero wasted words. Every word earns its place, though this conciseness comes at the cost of completeness.

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?

Given a creation tool with 6 parameters (1 required), 0% schema coverage, no annotations, but with an output schema, the description is inadequate. While the output schema might document return values, the description doesn't address critical context like parameter meanings, creation constraints, or how this tool fits within the Blender workflow alongside sibling tools. For a moderately complex creation operation, more guidance is needed.

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 0% schema description coverage for 6 parameters, the description provides no parameter information beyond the tool name implying 'primitive' is a parameter. It doesn't explain what 'primitive' means (e.g., cube, sphere, cylinder), what 'size', 'location', 'rotation', and 'scale' units or formats are, or that 'name' is optional. The description fails to compensate for the complete lack of schema documentation.

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 clearly states the verb ('Create') and resource ('primitive mesh object'), making the purpose immediately understandable. However, it doesn't differentiate from sibling tools like 'execute_ops' or 'select_objects' that might also create or modify objects, leaving some ambiguity about when this specific creation tool should be used versus alternatives.

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 provides no guidance on when to use this tool versus alternatives. With siblings like 'execute_ops' (which could execute arbitrary Blender operations) and 'set_transform' (which might modify existing objects), there's no indication whether this is the primary creation method or when other tools might be more appropriate. No exclusions or prerequisites are mentioned.

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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