Set the default value of a Blueprint node input pin in Unreal Engine using its registered node ID, pin name, and value string.
Set a default value on a Blueprint node's input pin.
Args: node_id: Registered node ID pin_name: Input pin name value: Default value as string
| Name | Required | Description | Default |
|---|---|---|---|
| value | Yes | ||
| node_id | Yes | ||
| pin_name | Yes |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
v0.0.2Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden. It implies mutation via 'Set a default value' but does not disclose side effects, whether the blueprint must be compiled or saved afterward, permission requirements, or reversibility.
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 short, front-loaded with the action, and uses a tight argument list with no wasted sentences. Every line contributes directly to invoking the tool.
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?
An output schema exists, so return values need not be explained. However, for a mutation tool with no annotations and 0% schema description coverage, the description remains thin on prerequisites and side effects, making it only minimally complete for correct invocation.
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 0%, so the description must compensate. It gives brief meanings for all three parameters, including the useful detail that node_id is a 'Registered node ID', but it does not explain formats, how to obtain the registered ID, or acceptable value forms.
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 states a specific verb and resource: setting a default value on a Blueprint node's input pin. It is clear enough to distinguish from generic node/pin tools, but it does not explicitly differentiate from close siblings such as ms_set_default or bp_connect_bp_pins.
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 only the argument list and gives no when-to-use guidance, no prerequisites for obtaining or registering node_id, and no indication of when another tool like bp_connect_bp_pins or ms_set_default would be preferred.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.