Start an asynchronous Play-In-Editor session to verify that gameplay logic executes at runtime, not just compiles.
Start PIE (play/simulate) asynchronously. Poll with ue5_read_pie_state until is_playing=true. Use to verify that logic actually RUNS, not just that it compiles. | 启动 PIE/Simulate（异步；用 ue5_read_pie_state 轮询确认）。
| Name | Required | Description | Default |
|---|---|---|---|
| mode | No | 'simulate' (default) | 'play' | 启动模式 |
Changes observed during successful MCP inspections.
v3.2.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden. It discloses that the operation is asynchronous, that it must be polled, and that it starts a play/simulate session. It does not mention side effects like needing to stop the session with ue5_stop_pie, but the async polling behavior is the most critical behavioral trait and it is clearly disclosed.
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?
Two sentences, front-loaded with the action and async behavior, then the polling instruction, then the purpose. The bilingual addition is compact and does not bloat the English content. Every sentence earns its place.
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?
For a tool with one optional parameter and no output schema, the description covers the start action, the async nature, the polling mechanism, and the intended use case. It does not mention how to stop the PIE session, but the sibling ue5_stop_pie exists and the polling instruction is sufficient for correct invocation. Minor gap: no mention of what happens if PIE is already running.
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 coverage is 100% and the only parameter (mode) is fully described in the schema with its allowed values and default. The description adds no additional parameter semantics, but the schema already carries the full burden. Baseline 3 is appropriate.
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 ('Start'), a specific resource ('PIE (play/simulate)'), and the async behavior. It also distinguishes itself from compile-only verification by saying 'Use to verify that logic actually RUNS, not just that it compiles.' This clearly differentiates it from sibling tools like ue5_compile_blueprint.
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 explicitly tells the agent when to use this tool: to verify logic runs, not just compiles. It also names the exact sibling to poll with (ue5_read_pie_state) and the condition to wait for (is_playing=true). This is explicit routing guidance with no ambiguity.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.