How do I use vtkapi-mcp?

1. Click on "Install Server". 2. Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state. 3. In the chat, type @ followed by the MCP server name and your instructions, e.g., "@vtkapi-mcp Validate VTK: vtkSphereSource()" That's it! The server will respond to your query, and you can continue using it as needed. Here is a step-by-step guide with screenshots.

vtkapi-mcp

by patrickoleary

Overview Schema Related Servers Score Discussions

Python

Local

VTK API Validation via MCP

Post-generation validation of VTK Python code using Model Context Protocol (MCP).

Overview

This module provides automatic validation of generated VTK code to catch API hallucinations:

✅ Direct API lookups - No vector search overhead, exact class/method verification
✅ Method existence validation - Detects when LLM invents non-existent methods
✅ Import validation - Verifies VTK classes are imported from correct modules
✅ Fast in-memory index - Loads ~2,900 VTK classes at startup
✅ Structured error reporting - Clear error messages with suggestions

Quick Start

1. Install the Package

From PyPI (recommended once published):

pip install vtkapi-mcp

For local development we standardize on uv to manage the virtualenv and extras:

uv venv .venv
source .venv/bin/activate
uv sync --extra dev      # runtime + pytest + ruff

Note: The 64 MB data/vtk-python-docs.jsonl file is required at runtime but is not bundled in the wheel. Place it under data/ (or pass --api-docs /path/to/file) before launching the MCP server.

Prefer automation? ./setup.sh now wraps the same uv workflow and accepts --dev to include the testing toolchain.

2. Test MCP Integration (Optional)

uv run python demo_mcp_integration.py

This runs a complete demo showing how to use vtkapi-mcp as an MCP server (not as standalone Python library). It demonstrates all 18 MCP tools and error detection.

3. Developer Workflow (uv-native)

Task	Command
Run unit + integration tests	`uv run pytest`
Run tests with coverage report	`uv run pytest --cov=vtkapi_mcp --cov-report=term-missing`
Run Ruff lint & format checks	`uv run ruff check` / `uv run ruff format --check`

These commands automatically reuse the .venv created via uv venv / uv sync. No manual activation is required.

3. Configure MCP Client

Add to your MCP settings (e.g., Claude Desktop config):

{
  "mcpServers": {
    "vtk-api": {
      "command": "python",
      "args": [
        "-m",
        "vtkapi_mcp",
        "--api-docs",
        "/absolute/path/to/vtkapi-mcp/data/vtk-python-docs.jsonl"
      ]
    }
  }
}

4. Use VTK Tools

The MCP server provides 18 tools for VTK API validation and lookup. See MCP Tools below.

Project Structure

Package Organization

vtkapi_mcp/
├── core/              # API indexing and data loading
│   └── api_index.py
├── validation/        # Code validation logic
│   ├── models.py
│   ├── validator.py
│   ├── import_validator.py
│   ├── class_validator.py
│   └── method_validator.py
├── server/           # MCP server implementation
│   ├── mcp_server.py
│   └── tools.py
└── utils/            # Utilities for parsing and search
    ├── extraction.py
    └── search.py

Supporting Files

File	Purpose
`demo_mcp_integration.py`	Demo showing proper MCP integration (not standalone)
`pyproject.toml`	Python package configuration and dependencies
`README.md`	This file

Data

File	Purpose	Size
`data/vtk-python-docs.jsonl`	VTK API documentation (~2,900 classes)	~64 MB

Architecture

VTKAPIIndex (vtkapi_mcp/core/api_index.py)

Fast in-memory index of all VTK classes and methods:

VTKAPIIndex
├── Classes Dict: {class_name → {module, methods, docs}}
├── Modules Dict: {module_name → [class_names]}
└── Load Time: <1 second for ~2,900 classes

Key Methods:

get_class_info(class_name) - Get module and documentation
search_classes(query) - Search by name or keyword
get_module_classes(module) - List classes in module
class_exists(class_name) - Check if class exists

VTKCodeValidator (vtkapi_mcp/validation/validator.py)

AST-based validation of generated Python code:

VTKCodeValidator
├── Parse Code: Uses Python's ast module
├── Extract VTK Usage:
│   ├── Import statements
│   ├── Class instantiations
│   └── Method calls
├── Validate Against Index:
│   ├── Check classes exist
│   ├── Check imports correct
│   └── Check methods exist
└── Generate Error Report

Validation Types:

Import Validation - Verifies module paths
Class Validation - Checks class existence
Method Validation - Detects hallucinated methods

MCP Tools Provided

When running as MCP server, provides these 18 tools:

1. `vtk_get_class_info`

Get complete information about a VTK class.

Input:

{
  "class_name": "vtkPolyDataMapper"
}

Output:

{
  "class_name": "vtkPolyDataMapper",
  "module": "vtkmodules.vtkRenderingCore",
  "content_preview": "vtkPolyDataMapper - map vtkPolyData to graphics primitives..."
}

2. `vtk_search_classes`

Search for VTK classes by name or keyword.

Input:

{
  "query": "reader",
  "limit": 5
}

Output:

[
  {
    "class_name": "vtkSTLReader",
    "module": "vtkmodules.vtkIOGeometry",
    "description": "Read ASCII or binary stereo lithography files."
  }
]

5. `vtk_validate_import`

Validate and correct VTK import statements.

Input:

{
  "import_statement": "from vtkmodules.vtkCommonDataModel import vtkPolyDataMapper"
}

Output:

{
  "valid": false,
  "message": "Incorrect module. 'vtkPolyDataMapper' is in 'vtkmodules.vtkRenderingCore'",
  "suggested": "from vtkmodules.vtkRenderingCore import vtkPolyDataMapper"
}

6. `vtk_get_method_info`

Get full information about a specific method including section context.

Input:

{
  "class_name": "vtkPolyDataMapper",
  "method_name": "SetInputData"
}

Output:

{
  "class_name": "vtkPolyDataMapper",
  "method_name": "SetInputData",
  "content": "SetInputData(vtkDataObject) - Set the input data...",
  "section": "Methods defined here"
}

7. `vtk_get_method_doc`

Get just the docstring for a specific method.

Input:

{
  "class_name": "vtkPolyDataMapper",
  "method_name": "SetInputData"
}

Output:

{
  "class_name": "vtkPolyDataMapper",
  "method_name": "SetInputData",
  "docstring": "SetInputData(vtkDataObject) - Set the input data...",
  "found": true
}

8. `vtk_get_class_doc`

Get the class documentation string.

Input:

{
  "class_name": "vtkPolyDataMapper"
}

Output:

{
  "class_name": "vtkPolyDataMapper",
  "class_doc": "vtkPolyDataMapper - map vtkPolyData to graphics primitives. Superclass: vtkMapper",
  "found": true
}

9. `vtk_get_class_synopsis`

Get a brief synopsis/summary of what a class does.

Input:

{
  "class_name": "vtkPolyDataMapper"
}

Output:

{
  "class_name": "vtkPolyDataMapper",
  "synopsis": "Maps polygonal data (vtkPolyData) to graphics primitives for rendering.",
  "found": true
}

10. `vtk_get_class_action_phrase`

Get the action phrase describing what a class does.

Input:

{
  "class_name": "vtkPolyDataMapper"
}

Output:

{
  "class_name": "vtkPolyDataMapper",
  "action_phrase": "polygon mapping",
  "found": true
}

11. `vtk_get_class_role`

Get the functional role/category of a class.

Input:

{
  "class_name": "vtkPolyDataMapper"
}

Output:

{
  "class_name": "vtkPolyDataMapper",
  "role": "rendering",
  "found": true
}

12. `vtk_get_class_visibility`

Get the visibility/exposure level of a class.

Input:

{
  "class_name": "vtkPolyDataMapper"
}

Output:

{
  "class_name": "vtkPolyDataMapper",
  "visibility": "likely",
  "found": true
}

13. `vtk_get_module_classes`

List all classes in a specific module.

Input:

{
  "module": "vtkmodules.vtkRenderingCore"
}

Output:

{
  "module": "vtkmodules.vtkRenderingCore",
  "classes": ["vtkActor", "vtkPolyDataMapper", ...],
  "count": 42
}

14. `vtk_get_class_module`

Return the vtkmodules.* import path for a given VTK class.

Input:

{
  "class_name": "vtkPolyDataMapper"
}

Output:

{
  "class_name": "vtkPolyDataMapper",
  "module": "vtkmodules.vtkRenderingCore",
  "found": true
}

15. `vtk_get_class_input_datatype`

Get the input data type for a VTK class.

Input:

{
  "class_name": "vtkPolyDataMapper"
}

Output:

{
  "class_name": "vtkPolyDataMapper",
  "input_datatype": "vtkPolyData",
  "found": true
}

16. `vtk_get_class_output_datatype`

Get the output data type for a VTK class.

Input:

{
  "class_name": "vtkContourFilter"
}

Output:

{
  "class_name": "vtkContourFilter",
  "output_datatype": "vtkPolyData",
  "found": true
}

17. `vtk_get_class_semantic_methods`

Get semantically tagged methods for a VTK class (input setters, output getters, configuration methods).

Input:

{
  "class_name": "vtkContourFilter"
}

Output:

{
  "class_name": "vtkContourFilter",
  "semantic_methods": {
    "input_setters": ["SetInputData", "SetInputConnection"],
    "output_getters": ["GetOutput", "GetOutputPort"],
    "configuration": ["SetValue", "SetNumberOfContours"]
  },
  "found": true
}

18. `vtk_is_a_class`

Check if a given name is a valid VTK class.

Input:

{
  "class_name": "vtkPolyDataMapper"
}

Output:

{
  "class_name": "vtkPolyDataMapper",
  "is_vtk_class": true
}

Benefits Over RAG Retrieval

Aspect	RAG Retrieval	MCP Validation
Speed	Vector search + reranking	Direct hash lookup (instant)
Accuracy	Semantic similarity (can drift)	Exact API match (100%)
Coverage	Top-K only (~10 results)	All ~2,900 classes available
Tokens	Consumes prompt tokens	Tool calls (minimal cost)
Errors	Silent hallucinations	Explicit error messages

Validation Examples

Example 1: Method Hallucination (CAUGHT ✅)

Generated Code:

stencil = vtkImageStencilToImage()
stencil.SetOutputWholeExtent([0, 10, 0, 10, 0, 10])  # ❌ Doesn't exist!

Validation Error:

UNKNOWN_METHOD: Method 'SetOutputWholeExtent' not found on class 'vtkImageStencilToImage'
Suggestion: Did you mean SetOutputOrigin or SetOutputSpacing?

Example 2: Wrong Import Module (CAUGHT ✅)

Generated Code:

from vtkmodules.vtkCommonDataModel import vtkPolyDataMapper  # ❌ Wrong module!

Validation Error:

IMPORT_ERROR: 'vtkPolyDataMapper' is not in module 'vtkmodules.vtkCommonDataModel'
Correct import: from vtkmodules.vtkRenderingCore import vtkPolyDataMapper

Example 3: Non-existent Class (CAUGHT ✅)

Generated Code:

converter = vtkImageDataToPolyDataConverter()  # ❌ Class doesn't exist!

Validation Error:

UNKNOWN_CLASS: Class 'vtkImageDataToPolyDataConverter' not found in VTK
Suggestion: Did you mean vtkImageDataGeometryFilter?

Data Source

Input: data/vtk-python-docs.jsonl

Each line is a VTK class documentation in JSON format:

{
  "class_name": "vtkPolyDataMapper",
  "module_name": "vtkmodules.vtkRenderingCore",
  "class_doc": "vtkPolyDataMapper - map vtkPolyData to graphics primitives. Superclass: vtkMapper",
  "synopsis": "Maps polygonal data (vtkPolyData) to graphics primitives for rendering.",
  "action_phrase": "polygon mapping",
  "role": "rendering",
  "visibility_score": "likely",
  "input_datatype": "vtkPolyData",
  "output_datatype": "",
  "semantic_methods": { "input_setters": [...], "output_getters": [...] },
  "structured_docs": { "sections": { ... } }
}

Coverage: ~2,900 VTK classes from VTK Python API

Future Enhancements

Method signature validation - Check parameter types and counts
Deprecation warnings - Flag deprecated VTK methods
Pipeline validation - Verify data flow compatibility
Auto-fix suggestions - Generate corrected code automatically
Performance profiling - Track validation overhead
Cache layer - Cache frequent lookups for speed

License

This is a standalone MCP server for VTK API validation. Extracted from the vtk-rag project.

Status: Production ready MCP server for VTK API validation.

Install Server

license - permissive license

quality

maintenance

How are these scores calculated?

Resources

GitHub Repository

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VTK API Validation via MCP

Overview

Quick Start

1. Install the Package

2. Test MCP Integration (Optional)

3. Developer Workflow (uv-native)

3. Configure MCP Client

4. Use VTK Tools

Project Structure

Package Organization

Supporting Files

Data

Architecture

VTKAPIIndex (vtkapi_mcp/core/api_index.py)

VTKCodeValidator (vtkapi_mcp/validation/validator.py)

MCP Tools Provided

1. vtk_get_class_info

2. vtk_search_classes

5. vtk_validate_import

6. vtk_get_method_info

7. vtk_get_method_doc

8. vtk_get_class_doc

9. vtk_get_class_synopsis

10. vtk_get_class_action_phrase

11. vtk_get_class_role

12. vtk_get_class_visibility

13. vtk_get_module_classes

14. vtk_get_class_module

15. vtk_get_class_input_datatype

16. vtk_get_class_output_datatype

17. vtk_get_class_semantic_methods

18. vtk_is_a_class

Benefits Over RAG Retrieval

Validation Examples

Example 1: Method Hallucination (CAUGHT ✅)

Example 2: Wrong Import Module (CAUGHT ✅)

Example 3: Non-existent Class (CAUGHT ✅)

Data Source

Future Enhancements

License

Resources

Looking for Admin?

Tools

Latest Blog Posts

MCP directory API

1. `vtk_get_class_info`

2. `vtk_search_classes`

5. `vtk_validate_import`

6. `vtk_get_method_info`

7. `vtk_get_method_doc`

8. `vtk_get_class_doc`

9. `vtk_get_class_synopsis`

10. `vtk_get_class_action_phrase`

11. `vtk_get_class_role`

12. `vtk_get_class_visibility`

13. `vtk_get_module_classes`

14. `vtk_get_class_module`

15. `vtk_get_class_input_datatype`

16. `vtk_get_class_output_datatype`

17. `vtk_get_class_semantic_methods`

18. `vtk_is_a_class`