blender-mcp

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set_node_input

Idempotent

Set default values for color, float, or vector inputs on any Blender shader node within a material, enabling precise control over material properties.

Instructions

Set a node input's default value (color, float, vector).

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": {
      "material": "<material>",
      "node": "<node>",
      "input": "<input>",
      "value": "<value>"
    },
    "name": "set_node_input"
  }
}

Input Schema

Name	Required	Description	Default
`node`	Yes
`input`	Yes
`value`	Yes
`material`	Yes

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Aug 10, 2026

TDQS

B3/5.0

Behavior3/5

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

The idempotentHint annotation already covers idempotency, and the description adds that the tool sets a default value rather than a current value, plus the allowed value types. However, it does not disclose potential side effects like whether setting a default value affects existing connections or whether it is limited to unconnected inputs.

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 a single, direct sentence with no filler. It front-loads the verb and object, making the intent immediately clear despite its brevity.

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?

The description is too sparse for a 4-parameter tool in a large family of node-related tools. It does not specify which node tree type (shader, geo, compositor) it applies to, nor how to reference nodes and inputs. The idempotent annotation and presence of an output schema are helpful, but the missing operational context is significant.

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?

Schema description coverage is 0%, and the description only hints at the `value` parameter by naming supported types. It does not explain `material`, `node`, or `input` (including whether `input` is a socket name or index), leaving most parameter semantics underspecified.

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 action ('Set') and the resource ('node input's default value'), and it lists supported value types (color, float, vector), making the core purpose unambiguous. It distinguishes from sibling tools like get_node_input or set_node_position, though it does not explicitly name 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?

No guidance is provided on when to use this tool versus alternatives such as set_geonode_input, set_comp_node_input, or connect_shader_nodes. The description does not mention prerequisites or the node tree context it applies to.

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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