643 MCP Builder Tools Guide 232ef699

Agent Builder MCP Tools - MCP Integration Guide

This guide explains how to use the new MCP integration tools in the agent builder MCP server.

Overview

The agent builder now supports registering external MCP servers as tool sources. This allows you to:

1. Register MCP servers (like tools) during agent building
2. Discover available tools from those servers
3. Use those tools in your agent nodes
4. Automatically generate mcp_servers.json configuration on export

New MCP Tools

add_mcp_server

Register an MCP server as a tool source for your agent.

Parameters:

• name (string, required): Unique name for the MCP server
• transport (string, required): Transport type - "stdio" or "http"
• command (string): Command to run (for stdio transport)
• args (string): JSON array of command arguments (for stdio)
• cwd (string): Working directory (for stdio)
• env (string): JSON object of environment variables (for stdio)
• url (string): Server URL (for http transport)
• headers (string): JSON object of HTTP headers (for http)
• description (string): Description of the MCP server

Example - STDIO:

{
  "name": "add_mcp_server",
  "arguments": {
    "name": "tools",
    "transport": "stdio",
    "command": "python",
    "args": "[\"mcp_server.py\", \"--stdio\"]",
    "cwd": "../tools",
    "description": "Aden tools for web search and file operations"
  }
}

Example - HTTP:

{
  "name": "add_mcp_server",
  "arguments": {
    "name": "remote-tools",
    "transport": "http",
    "url": "http://localhost:4001",
    "description": "Remote tool server"
  }
}

Response:

{
  "success": true,
  "server": {
    "name": "tools",
    "transport": "stdio",
    "command": "python",
    "args": ["mcp_server.py", "--stdio"],
    "cwd": "../tools",
    "description": "Aden tools..."
  },
  "tools_discovered": 6,
  "tools": [
    "web_search",
    "web_scrape",
    "file_read",
    "file_write",
    "pdf_read",
    "example_tool"
  ],
  "total_mcp_servers": 1,
  "note": "MCP server 'tools' registered with 6 tools. These tools can now be used in llm_tool_use nodes."
}

list_mcp_servers

List all registered MCP servers.

Parameters: None

Response:

{
  "mcp_servers": [
    {
      "name": "tools",
      "transport": "stdio",
      "command": "python",
      "args": ["mcp_server.py", "--stdio"],
      "cwd": "../tools",
      "description": "Aden tools..."
    }
  ],
  "total": 1
}

list_mcp_tools

List tools available from registered MCP servers.

Parameters:

• server_name (string, optional): Name of specific server to list tools from. If omitted, lists tools from all servers.

Example:

{
  "name": "list_mcp_tools",
  "arguments": {
    "server_name": "tools"
  }
}

Response:

{
  "success": true,
  "tools_by_server": {
    "tools": [
      {
        "name": "web_search",
        "description": "Search the web for information using Brave Search API...",
        "parameters": ["query", "num_results", "country"]
      },
      {
        "name": "web_scrape",
        "description": "Scrape and extract text content from a webpage...",
        "parameters": ["url", "selector", "include_links", "max_length"]
      }
    ]
  },
  "total_tools": 6,
  "note": "Use these tool names in the 'tools' parameter when adding llm_tool_use nodes"
}

remove_mcp_server

Remove a registered MCP server.

Parameters:

• name (string, required): Name of the MCP server to remove

Example:

{
  "name": "remove_mcp_server",
  "arguments": {
    "name": "tools"
  }
}

Response:

{
  "success": true,
  "removed": "tools",
  "remaining_servers": 0
}

Workflow Example

Here's a complete workflow for building an agent with MCP tools:

1. Create Session

{
  "name": "create_session",
  "arguments": {
    "name": "web-research-agent"
  }
}

2. Register MCP Server

{
  "name": "add_mcp_server",
  "arguments": {
    "name": "tools",
    "transport": "stdio",
    "command": "python",
    "args": "[\"mcp_server.py\", \"--stdio\"]",
    "cwd": "../tools"
  }
}

3. List Available Tools

{
  "name": "list_mcp_tools",
  "arguments": {
    "server_name": "tools"
  }
}

4. Set Goal

{
  "name": "set_goal",
  "arguments": {
    "goal_id": "web-research",
    "name": "Web Research Agent",
    "description": "Search the web and summarize findings",
    "success_criteria": "[{\"id\": \"search-success\", \"description\": \"Successfully retrieve search results\", \"metric\": \"results_count\", \"target\": \">= 3\", \"weight\": 1.0}]"
  }
}

5. Add Node with MCP Tool

{
  "name": "add_node",
  "arguments": {
    "node_id": "web-searcher",
    "name": "Web Search",
    "description": "Search the web for information",
    "node_type": "llm_tool_use",
    "input_keys": "[\"query\"]",
    "output_keys": "[\"search_results\"]",
    "system_prompt": "Search for {query} using the web_search tool",
    "tools": "[\"web_search\"]"
  }
}

Note: web_search is now available because we registered the tools MCP server!

6. Export Agent

{
  "name": "export_graph",
  "arguments": {}
}

The export will create:

• exports/web-research-agent/agent.json - Agent specification
• exports/web-research-agent/README.md - Documentation
• exports/web-research-agent/mcp_servers.json - MCP server configuration ✨

MCP Configuration File

When you export an agent with registered MCP servers, an mcp_servers.json file is automatically created:

{
  "servers": [
    {
      "name": "tools",
      "transport": "stdio",
      "command": "python",
      "args": ["mcp_server.py", "--stdio"],
      "cwd": "../tools",
      "description": "Aden tools for web search and file operations"
    }
  ]
}

This file is automatically loaded by the AgentRunner when the agent is executed, making the MCP tools available at runtime.

Using the Exported Agent

Once exported, load and run the agent normally:

from framework.runner.runner import AgentRunner

# Load agent - MCP servers auto-load from mcp_servers.json
runner = AgentRunner.load("exports/web-research-agent")

# Run with input
result = await runner.run({"query": "latest AI breakthroughs"})

# The web_search tool from tools is automatically available!

Benefits

1. Discoverable Tools: See what tools are available before using them
2. Validation: Connection is tested when registering the server
3. Automatic Configuration: No manual file editing required
4. Documentation: README includes MCP server information
5. Runtime Ready: Exported agents work immediately with configured tools

Common MCP Servers

tools

Provides:

• web_search - Brave Search API integration
• web_scrape - Web page content extraction
• file_read / file_write - File operations
• pdf_read - PDF text extraction

Custom MCP Servers

You can register any MCP server that follows the Model Context Protocol specification.

Troubleshooting

"Failed to connect to MCP server"

• Verify the command and args are correct
• Check that the server is accessible at the specified path/URL
• Ensure any required environment variables are set
• For STDIO: verify the command can be executed from the cwd
• For HTTP: verify the server is running and accessible

Tools not appearing

• Use list_mcp_tools to verify tools were discovered
• Check the tool names match exactly (case-sensitive)
• Ensure the MCP server is still registered (list_mcp_servers)

Export doesn't include mcp_servers.json

• Verify you registered at least one MCP server
• Check get_session_status to see mcp_servers_count > 0
• Re-export the agent after registering servers

Credential Validation

When adding nodes with tools that require API keys (like web_search), the agent builder automatically validates that the required credentials are available.

How It Works

When you call add_node or update_node with a tools parameter, the agent builder:

1. Checks which tools require credentials (e.g., web_search requires BRAVE_SEARCH_API_KEY)
2. Validates those credentials are set in the environment or .env file
3. Returns an error if any credentials are missing

Missing Credentials Error

If credentials are missing, you'll receive a response like:

{
  "valid": false,
  "errors": ["Missing credentials for tools: ['BRAVE_SEARCH_API_KEY']"],
  "missing_credentials": [
    {
      "credential": "brave_search",
      "env_var": "BRAVE_SEARCH_API_KEY",
      "tools_affected": ["web_search"],
      "help_url": "https://brave.com/search/api/",
      "description": "API key for Brave Search"
    }
  ],
  "action_required": "Add the credentials to your .env file and retry",
  "example": "Add to .env:\nBRAVE_SEARCH_API_KEY=your_key_here",
  "message": "Cannot add node: missing API credentials. Add them to .env and retry this command."
}

Fixing Credential Errors

1. Get the required API key from the URL in help_url

2. Add it to your environment:

   # Option 1: Export directly
   export BRAVE_SEARCH_API_KEY=your-key-here
   
   # Option 2: Add to tools/.env
   echo "BRAVE_SEARCH_API_KEY=your-key-here" >> tools/.env
   

3. Retry the add_node command

Required Credentials by Tool

Note: The MCP server itself requires ANTHROPIC_API_KEY at startup for LLM operations.