Isaac Sim MCP Server

by whats2000

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reload_script

Reload a Python controller file to apply on-disk edits. Recompiles linked Action Graph ScriptNodes, or re-executes standalone scripts for iteration.

Instructions

Reload a Python controller from a file on disk.

Two modes, chosen automatically:

If any Action-Graph ScriptNode references this file (inputs:scriptPath), those ScriptNodes are force-recompiled so your on-disk edits take effect on the running graph. This is how you iterate on a ScriptNode controller.
Otherwise the file is (re-)executed as a standalone controller, the way you would use execute_script for code longer than ~20 lines.

Workflow:

Write the controller as a .py file (attach via create_action_graph script_file=... for ScriptNode use)
reload_script to load / recompile it
step_simulation to debug (frozen timeline) or play for a ScriptNode demo
Edit the file and reload_script again to iterate

The file's directory is auto-added to sys.path.

Args: file_path: Path to the Python file on disk. script_file: Alias for file_path. create_action_graph names this argument script_file, and an unknown argument is dropped silently rather than rejected, so both spellings are accepted here instead of one of them quietly doing nothing. module_name: Optional module name to reload (e.g. 'my_controller').

Input Schema

TableJSON Schema

Name	Required	Description	Default
`file_path`	No
`module_name`	No
`script_file`	No

Output Schema

TableJSON Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed5 schema fields changedv0.6.1Sep 22, 2026

addedInput schema / properties / file_path / anyOf

Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

addedInput schema / properties / file_path / default
```
Added value: +null
```
removedInput schema / properties / file_path / type
```
Removed value: -"string"
```

addedInput schema / properties / script_file

Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "title": "Script File"
+}

removedInput schema / required
```
Removed value: -[
-  "file_path"
-]
```

First observedv0.1.0Jun 4, 2026

TDQS

A5/5.0

Behavior5/5

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

With no annotations at all, the description fully carries the behavioral burden. It discloses automatic mode selection, force-recompilation of ScriptNodes, standalone re-execution, sys.path modification, and the silent dropping of unknown arguments. These are important non-obvious behaviors beyond the schema.

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 well structured with a clear opening, mode explanation, workflow list, and argument details. Every section earns its place, and the most important information is front-loaded. Length is justified by the tool's dual-mode complexity.

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?

Given the tool's dual-mode nature, absence of annotations, and 0% schema description coverage, the description covers everything needed: when it applies, how it behaves, required workflow context, and parameter semantics. The presence of an output schema means return-value documentation is not required here.

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

Parameters5/5

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

Schema description coverage is 0%, but the description compensates fully. It explains file_path, script_file as an alias, module_name's optional role, and even the reason both aliases are accepted. This is more useful than typical parameter documentation.

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?

The description begins with a specific verb and object: 'Reload a Python controller from a file on disk.' It then clearly separates two modes, making it easy to distinguish from siblings like execute_script and create_action_graph. The mention of ScriptNode recompilation gives precise resource context.

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

Usage Guidelines5/5

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

The description explicitly states when each mode applies and provides a workflow linking reload_script to create_action_graph, step_simulation, and play_simulation. It also references execute_script as the alternative for standalone execution, giving an agent clear decision criteria.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.