README.md•7.14 kB
# char-index-mcp
A Model Context Protocol (MCP) server providing **character-level index-based string manipulation**. Perfect for test code generation where precise character positioning matters.
[](https://smithery.ai/server/char-index-mcp)
[](https://opensource.org/licenses/MIT)
[](https://pypi.org/project/char-index-mcp/)
[](https://pypi.org/project/char-index-mcp/)
> This project was created with Claude AI.
## 🎯 Why This Exists
LLMs generate text token-by-token and struggle with exact character counting. When generating test code with specific length requirements or validating string positions, you need precise index-based tools. This MCP server solves that problem.
## ✨ Features (12 Tools)
### 🔍 Character & Substring Finding (4 tools)
- `find_nth_char` - Find nth occurrence of a character
- `find_all_char_indices` - Find all indices of a character
- `find_nth_substring` - Find nth occurrence of a substring
- `find_all_substring_indices` - Find all occurrences of a substring
### ✂️ Splitting (1 tool)
- `split_at_indices` - Split string at multiple positions
### ✏️ String Modification (3 tools)
- `insert_at_index` - Insert text at specific position
- `delete_range` - Delete characters in range
- `replace_range` - Replace range with new text
### 🛠️ Utilities (3 tools)
- `find_regex_matches` - Find regex pattern matches with positions
- `extract_between_markers` - Extract text between two markers
- `count_chars` - Character statistics (total, letters, digits, etc.)
### 📦 Batch Processing (1 tool)
- `extract_substrings` - Extract one or more substrings (unified tool)
## 🚀 Installation
### Option 1: Using uvx (Recommended)
No installation required! Just configure and run:
```bash
# Test it works
uvx char-index-mcp --help
```
### Option 2: From PyPI
```bash
pip install char-index-mcp
```
### Option 3: From Source
```bash
git clone https://github.com/agent-hanju/char-index-mcp.git
cd char-index-mcp
pip install -e .
```
## 🔧 Configuration
### Claude Desktop
**macOS**: `~/Library/Application Support/Claude/claude_desktop_config.json`
**Windows**: `%APPDATA%\Claude\claude_desktop_config.json`
#### Using uvx (Recommended)
```json
{
"mcpServers": {
"char-index": {
"command": "uvx",
"args": ["char-index-mcp"]
}
}
}
```
#### Using pip install
```json
{
"mcpServers": {
"char-index": {
"command": "char-index-mcp"
}
}
}
```
### Claude Code
```bash
# Using uvx (recommended)
claude mcp add char-index '{"command":"uvx","args":["char-index-mcp"]}'
# Using pip install
claude mcp add char-index '{"command":"char-index-mcp"}'
```
### Cursor
Add to `~/.cursor/mcp.json`:
#### Using uvx (Recommended)
```json
{
"mcpServers": {
"char-index": {
"command": "uvx",
"args": ["char-index-mcp"]
}
}
}
```
#### Using pip install
```json
{
"mcpServers": {
"char-index": {
"command": "char-index-mcp"
}
}
}
```
## 📖 Usage Examples
### Finding Characters
```python
# Find 3rd occurrence of 'l'
find_nth_char("hello world", "l", 3) # Returns: 9
# Find all occurrences of 'l'
find_all_char_indices("hello world", "l") # Returns: [2, 3, 9]
```
### Working with Substrings
```python
# Find 2nd "hello"
find_nth_substring("hello hello world", "hello", 2) # Returns: 6
# Find all occurrences
find_all_substring_indices("hello hello world", "hello") # Returns: [0, 6]
```
### String Manipulation
```python
# Insert comma after "hello"
insert_at_index("hello world", 5, ",") # Returns: "hello, world"
# Delete " world"
delete_range("hello world", 5, 11) # Returns: "hello"
# Replace "world" with "Python"
replace_range("hello world", 6, 11, "Python") # Returns: "hello Python"
```
### Splitting & Extracting
```python
# Split at multiple positions
split_at_indices("hello world", [2, 5, 8]) # Returns: ["he", "llo", " wo", "rld"]
# Extract single character
extract_substrings("hello", [{"start": 1, "end": 2}])
# Returns: [{"start": 1, "end": 2, "substring": "e", "length": 1}]
# Batch extraction
extract_substrings("hello world", [
{"start": 0, "end": 5},
{"start": 6, "end": 11}
])
# Returns: [
# {"start": 0, "end": 5, "substring": "hello", "length": 5},
# {"start": 6, "end": 11, "substring": "world", "length": 5}
# ]
```
### Pattern Matching
```python
# Find all numbers with their positions
find_regex_matches("test123abc456", r"\d+")
# Returns: [
# {"start": 4, "end": 7, "match": "123"},
# {"start": 10, "end": 13, "match": "456"}
# ]
```
### Extracting Text
```python
# Extract content between markers
extract_between_markers("start[content]end", "[", "]", 1)
# Returns: {
# "content": "content",
# "content_start": 6,
# "content_end": 13,
# "full_start": 5,
# "full_end": 14
# }
```
## 🧪 Development
```bash
# Clone the repository
git clone https://github.com/agent-hanju/char-index-mcp.git
cd char-index-mcp
# Install in development mode
pip install -e ".[dev]"
# Run tests
pytest
# Run with coverage
pytest --cov=char_index_mcp --cov-report=term-missing
```
## 🎯 Use Cases
1. **Test Code Generation**: Generate strings with exact character counts
2. **Data Processing**: Split/extract data at precise positions
3. **Text Formatting**: Insert/delete/replace at specific indices
4. **Pattern Analysis**: Find and extract pattern matches with positions
5. **LLM Response Parsing**: Extract content between XML tags by position
## 📝 Example: Test Code Generation
```python
# Ask Claude: "Generate a test string that's exactly 100 characters long"
# Claude can use count_chars() to verify the exact length
# Ask: "Find where the 5th comma is in this CSV line"
# Claude can use find_nth_char(csv_line, ",", 5)
# Ask: "Split this string at characters 10, 25, and 50"
# Claude can use split_at_indices(text, [10, 25, 50])
# Ask: "Extract the text between the 2nd <thinking> and </thinking> tags"
# Claude can use extract_between_markers(text, "<thinking>", "</thinking>", 2)
```
## 🤝 Contributing
Contributions are welcome! Please:
1. Fork the repository
2. Create a feature branch
3. Add tests for new functionality
4. Submit a pull request
## 📄 License
MIT License - see LICENSE file for details
## 🔗 Related Projects
- [mcp-character-counter](https://github.com/webreactiva-devs/mcp-character-counter) - Character counting & analysis
- [mcp-wordcounter](https://github.com/qpd-v/mcp-wordcounter) - Word & character counting for files
- [text-master-mcp](https://github.com/very99/text-master-mcp) - Comprehensive text processing toolkit
## 📮 Contact
For issues, questions, or suggestions, please open an issue on GitHub.
---
**Note**: This is the first MCP server specifically designed for index-based string manipulation. All other text MCP servers focus on counting, case conversion, or encoding - not precise character positioning.