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create_game_instance_class_bp

Idempotent

Create a Blueprint subclass of UGameInstance to define custom game instance logic. Registers the asset and marks it dirty for saving, with idempotent re-runs.

Instructions

Create a Blueprint subclass of UGameInstance, registered and marked dirty but not saved (persist it with save_asset). Idempotent on re-run: a Blueprint already at that path whose parent derives from parent_class is returned with already_exists=true; one with another parent is an error and is left untouched. parent_class is read off the Blueprint.

Returns: { asset_name, asset_path, package_class, parent_class, already_exists }

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
forceNoOptional. This command is REFUSED while a Play-in-Editor session is running: it either compiles a Blueprint (the reinstancer can retain a world, and CheckForWorldGCLeaks is Fatal -- it KILLS the editor) or writes to disk (Editor.AllowSavingAssetsDuringPIE=0 makes the engine refuse the write, so it would report success without writing a byte). Stop PIE and retry instead; force=true runs it anyway, at your own risk.
asset_nameYesName for the new Blueprint asset.
package_pathNoTarget content folder; defaults to /Game/MCP.
parent_classYesParent class name; must derive from UGameInstance.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.1.0

TDQS

A4.4/5.0
Behavior5/5

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

Annotations already declare mutation, non-destructive and idempotent, and the description adds real behavior beyond them: the asset is left unsaved on disk, re-runs return already_exists=true, a mismatched parent is an error and leaves the asset untouched, and parent_class is derived from the Blueprint rather than trusted from input. That is exactly the extra context an agent needs for a mutating tool.

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?

Three tightly packed sentences plus a compact returns line, front-loaded with purpose and then idempotency/error behavior. Dense but every clause carries information; no filler.

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

Completeness5/5

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

For a creation tool with no output schema, the description supplies the return shape, the persistence obligation, the idempotent re-run contract, and the failure case, while annotations cover the safety profile and the schema covers the PIE/force hazard. Nothing an agent needs to call this correctly is missing.

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

Parameters3/5

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

Schema description coverage is 100%, including a detailed 'force'/PIE-refusal explanation, so the schema carries the parameter burden. The description only adds the parent_class-derived-from-Blueprint note, which is closer to return-value semantics than parameter semantics; baseline 3 applies.

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

Purpose5/5

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

States a specific verb + resource ('Create a Blueprint subclass of UGameInstance') and immediately scopes it ('registered and marked dirty but not saved'), which separates it from plain asset-creation siblings. The named follow-up (save_asset) tells the agent what this tool does not do.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives clear operating context: persist via save_asset, re-run is safe because it is idempotent, and a path collision with a different parent is an error. It stops short of explicitly comparing against the other create_*_class_bp siblings, so the agent still infers which class creator to pick, but the when-to-use/persist guidance is concrete.

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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