piece_instance
Instance a piece template into the open scene and bind data (art / color / label) via the template's set_data(). Undoable node authoring. Optionally place_on a board cell in the same call (reparent + snap via board_place). Reports which data keys bound and which had no matching slot.
This record as markdown: /tools/breakpoint-mcp/piece-instance.md
What piece_instance does on Breakpoint
AI agents use piece_instance to create or update resources in Breakpoint, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Breakpoint environment.
| Parameter | Type | Required | Description |
|---|---|---|---|
data | object | Yes | Slot name → value (art takes a res:// path; color a #RRGGBB; label a string) |
name | string | — | Optional node name for the instance |
parent | string | Yes | Node path to parent the instance under (in the open scene); "." for the root |
face_up | boolean | — | Show the face (default true); false shows the back on two-sided pieces |
persist | boolean | — | Bake the bound data into the saved scene by enabling Editable Children on the instance (default false = runtime-bound only, reverts on reload) |
place_on | object | — | Optionally place the new piece on a board cell in the same call |
position | object | — | Local position of the instance (ignored when place_on snaps it to a cell) |
template_path | string | Yes | Piece template scene, e.g. res://ui/pieces/Piece.tscn |
Parameters from the server's own tool schema.
Why piece_instance is rated Medium
This tool creates new instances and modifies scene state by binding data to templates. These are creation and modification operations without permanent destruction. The reversibility ("Undoable") and the fact that it operates within a scene authoring context (likely a game or animation editor) place it in the Write category.
From the tool's definition The tool "instances a piece template into the open scene and bind data" and is described as "Undoable node authoring." It creates new scene objects and modifies data bindings, which are Write operations.
Risk signalsHigh parameter count (15 properties)
Attacks that exploit this kind of access
The rule that runs piece_instance safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Breakpoint, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For piece_instance, this is the rule to start with:
piece_instance stays usable, but capped: an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Breakpoint, apply this rule, and every piece_instance call is checked against it from then on.
Questions about piece_instance
Instance a piece template into the open scene and bind data (art / color / label) via the template's set_data(). Undoable node authoring. Optionally place_on a board cell in the same call (reparent + snap via board_place). Reports which data keys bound and which had no matching slot. It is categorised as a Write tool in the Breakpoint MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
piece_instance accepts 8 parameters: data, name, parent, face_up, persist, place_on, position, template_path. Required: data, parent, template_path. The full parameter table on this page comes from the server's own tool schema.
Register the Breakpoint MCP server in PolicyLayer and add a rule for piece_instance: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Breakpoint. Nothing to install.
piece_instance is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the piece_instance rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for piece_instance. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
piece_instance is provided by the Breakpoint MCP server (breakpoint-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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