Content
# MCP Tool Chainer
[](https://thirdstrandstudio.com/products/mcp-chain)
An MCP (Model Context Protocol) server that chains calls to other MCP tools, reducing token usage by allowing sequential tool execution with result passing.
Designed to solve [https://github.com/modelcontextprotocol/specification/issues/215](https://github.com/modelcontextprotocol/specification/issues/215)
Step function like JSON paths:
## Features
- Chain multiple MCP tools together in sequence
- Pass results from one tool as input to another tool using `CHAIN_RESULT` placeholder
- Filter and extract specific data using JsonPath with `inputPath` and `outputPath` parameters
- Automatic tool discovery from configured MCP servers
- Minimal token usage compared to individual tool calls
## Tools
This server implements the following MCP tools:
1. `mcp_chain` - Chain together multiple MCP servers
2. `chainable_tools` - Discover tools from all MCP servers so the mcp_chain tool can be used
3. `discover_tools` - Rediscover tools from all MCP servers
## Installation
### Prerequisites
* Node.js (v16 or later)
* npm
### Installing from npm
```bash
# Install
npm install @thirdstrandstudio/mcp-tool-chainer
# Or use with npx directly
npx -y @thirdstrandstudio/mcp-tool-chainer
```
### Installing from source
```bash
# Clone the repository
git clone https://github.com/thirdstrandstudio/mcp-tool-chainer.git
cd mcp-tool-chainer
# Install dependencies
npm install
# Build the package
npm run build
```
## Usage with Claude Desktop, Cursor etc
ENSURE IT IS THE LAST MCP TO RUN OTHERWISE IT WILL HAVE TO RUN DISCOVERY AGAIN
Add the following to your `claude_desktop_config.json` or `mcp.json`:
### If installed from npm globally
```json
{
"mcpServers": {
"mcp_tool_chainer": {
"command": "npx",
"args": ["-y", "@thirdstrandstudio/mcp-tool-chainer", "`claude_desktop_config.json` or `mcp.json`"],
"env": {}
}
}
}
```
### If installed from source
```json
{
"mcpServers": {
"mcp_tool_chainer": {
"command": "node",
"args": ["/path/to/mcp-tool-chainer/dist/index.js", "`claude_desktop_config.json` or `mcp.json`"],
"env": {}
}
}
}
```
Replace `/path/to/mcp-tool-chainer` with the actual path to your repository.
## Examples
### Chain Browser and XPath Tools
```javascript
// Fetch a webpage and then extract specific content with XPath
const result = await callTool("mcp_chain", {
"mcpPath": [
{
"toolName": "mcp_browser_mcp_fetch_url",
"toolArgs": "{\"url\": \"https://example.com\"}"
},
{
"toolName": "mcp_xpath_xpath",
"toolArgs": "{\"xml\": CHAIN_RESULT, \"query\": \"//h1\"}"
}
]
});
```
### Using JsonPath with InputPath and OutputPath
```javascript
// Fetch a webpage, extract specific content with XPath, then extract part of the result
const result = await callTool("mcp_chain", {
"mcpPath": [
{
"toolName": "mcp_fetch_fetch",
"toolArgs": "{\"url\": \"https://api.example.com/data\"}"
},
{
"toolName": "web_search",
"toolArgs": "{\"search_term\": CHAIN_RESULT}",
"inputPath": "$.results[0].title", // Extract only the first result's title from previous output
"outputPath": "$.snippets[*].text" // Extract only the text snippets from the search results
},
{
"toolName": "another_tool",
"toolArgs": "{\"content\": CHAIN_RESULT}"
}
]
});
```
## JsonPath Support
MCP Tool Chainer now supports AWS Step Functions-style InputPath and OutputPath features:
- **inputPath**: JsonPath expression to extract specific portions of the input before passing to a tool
- **outputPath**: JsonPath expression to extract specific portions of the output before passing to the next tool
These features work only when the input/output is valid JSON. If JsonPath extraction fails, the original input/output is used.
For JsonPath syntax reference, see [JsonPath Syntax](https://goessner.net/articles/JsonPath/).
## Benefits
- **Reduced Token Usage**: By chaining tools together, you avoid sending large intermediate results back to the LLM
- **Simplified Workflows**: Create complex data processing pipelines with a single tool call
- **Improved Performance**: Reduce latency by minimizing round-trips between the LLM and tools
- **Precise Data Flow Control**: Extract only the data you need with JsonPath expressions
## Development
```bash
# Install dependencies
npm install
# Start the server
node dist/index.js config.json
# List available tools
node dist/index.js config.json discover_tools
```
## License
This MCP server is licensed under the MIT License.
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Created by [Third Strand Studio](https://thirdstrandstudio.com/products/mcp-chain)
