Connecting to MCP Servers

Overview

Bifrost can connect to any MCP-compatible server to discover and execute tools. Each connection is called an MCP Client in Bifrost terminology.

Connection Types

Bifrost supports three connection protocols, each with different authentication options:

Type	Description	Best For	Auth Support
STDIO	Spawns a subprocess and communicates via stdin/stdout	Local tools, CLI utilities, scripts	None
HTTP	Sends requests to an HTTP endpoint	Remote APIs, microservices, cloud functions	Headers, OAuth 2.0
SSE	Server-Sent Events for persistent connections	Real-time data, streaming tools	Headers, OAuth 2.0

STDIO Connections

STDIO connections launch external processes and communicate via standard input/output. Best for local tools and scripts.

{
  "name": "filesystem",
  "connection_type": "stdio",
  "stdio_config": {
    "command": "npx",
    "args": ["-y", "@anthropic/mcp-filesystem"],
    "envs": ["HOME", "PATH"]
  },
  "tools_to_execute": ["*"]
}

Use Cases:

Local filesystem operations
Python/Node.js MCP servers
CLI utilities and scripts
Database tools with local credentials

Docker Users: When running Bifrost in Docker, STDIO connections may not work if the required commands (e.g., npx, python) are not installed in the container. For STDIO-based MCP servers, build a custom Docker image that includes the necessary dependencies, or use HTTP/SSE connections to externally hosted MCP servers.

HTTP Connections

HTTP connections communicate with MCP servers via HTTP requests. Ideal for remote services and microservices. HTTP connections support two authentication methods:

Header-based authentication: Static headers (API keys, custom tokens)
OAuth 2.0: Dynamic token-based authentication with automatic token refresh

Header-Based Authentication

Use static headers for API keys and custom authentication tokens:

{
  "name": "web-search",
  "connection_type": "http",
  "connection_string": "https://mcp-server.example.com/mcp",
  "auth_type": "headers",
  "headers": {
    "Authorization": "Bearer your-api-key",
    "X-Custom-Header": "value"
  },
  "tools_to_execute": ["*"]
}

Use Cases:

Static API keys
Bearer token authentication
Custom header-based auth schemes

OAuth 2.0 Authentication

Use OAuth 2.0 for secure, user-based authentication with automatic token refresh:

{
  "name": "web-search",
  "connection_type": "http",
  "connection_string": "https://mcp-server.example.com/mcp",
  "auth_type": "oauth",
  "oauth_config": {
    "client_id": "your-client-id",
    "client_secret": "your-client-secret",
    "authorize_url": "https://auth.example.com/authorize",
    "token_url": "https://auth.example.com/token",
    "scopes": ["read", "write"]
  },
  "tools_to_execute": ["*"]
}

Features:

Automatic token refresh before expiration
PKCE support for public clients
Dynamic client registration (RFC 7591)
OAuth discovery from server URLs

→ Learn more about OAuth authentication → Use Cases:

User-delegated access
Third-party service integrations
Secure credential management
Compliance with OAuth 2.0 standards

Overall HTTP Use Cases:

Remote API integrations
Cloud-hosted MCP services
Microservice architectures
Third-party tool providers

SSE Connections

Server-Sent Events (SSE) connections provide real-time, persistent connections to MCP servers. Like HTTP connections, SSE supports both header-based and OAuth authentication.

Header-Based Authentication

{
  "name": "live-data",
  "connection_type": "sse",
  "connection_string": "https://stream.example.com/mcp/sse",
  "auth_type": "headers",
  "headers": {
    "Authorization": "Bearer your-api-key"
  },
  "tools_to_execute": ["*"]
}

OAuth 2.0 Authentication

{
  "name": "live-data",
  "connection_type": "sse",
  "connection_string": "https://stream.example.com/mcp/sse",
  "auth_type": "oauth",
  "oauth_config": {
    "client_id": "your-client-id",
    "authorize_url": "https://auth.example.com/authorize",
    "token_url": "https://auth.example.com/token",
    "scopes": ["stream:read"]
  },
  "tools_to_execute": ["*"]
}

Use Cases:

Real-time market data
Live system monitoring
Event-driven workflows
User-authenticated streaming connections

→ Learn more about OAuth authentication →

Gateway Setup

Web UI
API
config.json

Adding an MCP Client

Navigate to MCP Gateway in the sidebar - you’ll see a table of all registered servers

Click New MCP Server button to open the creation form
Fill in the connection details:

Fields:

Name: Unique identifier (no spaces or hyphens, ASCII only)
Connection Type: STDIO, HTTP, or SSE
For STDIO: Command, arguments, and environment variables
For HTTP/SSE: Connection URL

Click Create to connect

Viewing and Managing Connected Tools

Once connected, click on any client row to open the configuration sheet:

Here you can:

View all discovered tools with their descriptions and parameters
Enable/disable individual tools via toggle switches
Configure auto-execution for specific tools
Edit custom headers for HTTP/SSE connections
View the full connection configuration as JSON

Add STDIO Client

curl -X POST http://localhost:8080/api/mcp/client \
  -H "Content-Type: application/json" \
  -d '{
    "name": "filesystem",
    "connection_type": "stdio",
    "stdio_config": {
      "command": "npx",
      "args": ["-y", "@anthropic/mcp-filesystem"],
      "envs": ["HOME", "PATH"]
    },
    "tools_to_execute": ["*"]
  }'

Add HTTP Client

curl -X POST http://localhost:8080/api/mcp/client \
  -H "Content-Type: application/json" \
  -d '{
    "name": "web_search",
    "connection_type": "http",
    "connection_string": "http://localhost:3001/mcp",
    "tools_to_execute": ["*"]
  }'

Add SSE Client

curl -X POST http://localhost:8080/api/mcp/client \
  -H "Content-Type: application/json" \
  -d '{
    "name": "realtime_data",
    "connection_type": "sse",
    "connection_string": "https://api.example.com/mcp/sse",
    "tools_to_execute": ["*"]
  }'

List All Clients

curl http://localhost:8080/api/mcp/clients

Response:

[
  {
    "config": {
      "id": "abc123",
      "name": "filesystem",
      "connection_type": "stdio",
      "stdio_config": {
        "command": "npx",
        "args": ["-y", "@anthropic/mcp-filesystem"]
      }
    },
    "tools": [
      {"name": "read_file", "description": "Read contents of a file"},
      {"name": "write_file", "description": "Write contents to a file"},
      {"name": "list_directory", "description": "List directory contents"}
    ],
    "state": "connected"
  }
]

Configure MCP clients in your config.json:

{
  "mcp": {
    "client_configs": [
      {
        "name": "filesystem",
        "connection_type": "stdio",
        "is_ping_available": true,
        "stdio_config": {
          "command": "npx",
          "args": ["-y", "@anthropic/mcp-filesystem"],
          "envs": ["HOME", "PATH"]
        },
        "tools_to_execute": ["*"]
      },
      {
        "name": "web_search",
        "connection_type": "http",
        "connection_string": "env.WEB_SEARCH_MCP_URL",
        "is_ping_available": false,
        "tools_to_execute": ["search", "fetch_url"]
      },
      {
        "name": "database",
        "connection_type": "sse",
        "connection_string": "https://db-mcp.example.com/sse",
        "is_ping_available": true,
        "tools_to_execute": []
      }
    ]
  }
}

Use env.VARIABLE_NAME syntax to reference environment variables for sensitive values like URLs with API keys.

Go SDK Setup

Configure MCP in your Bifrost initialization:

package main

import (
    "context"
    bifrost "github.com/maximhq/bifrost/core"
    "github.com/maximhq/bifrost/core/schemas"
)

func main() {
    mcpConfig := &schemas.MCPConfig{
        ClientConfigs: []schemas.MCPClientConfig{
            {
                Name:             "filesystem",
                ConnectionType:   schemas.MCPConnectionTypeSTDIO,
                IsPingAvailable:  true,  // Use lightweight ping for health checks
                StdioConfig: &schemas.MCPStdioConfig{
                    Command: "npx",
                    Args:    []string{"-y", "@anthropic/mcp-filesystem"},
                    Envs:    []string{"HOME", "PATH"},
                },
                ToolsToExecute: []string{"*"},
            },
            {
                Name:             "web_search",
                ConnectionType:   schemas.MCPConnectionTypeHTTP,
                ConnectionString: bifrost.Ptr("http://localhost:3001/mcp"),
                IsPingAvailable:  false,  // Use listTools for health checks
                ToolsToExecute:   []string{"search", "fetch_url"},
            },
        },
    }

    client, err := bifrost.Init(context.Background(), schemas.BifrostConfig{
        Account:   account,
        MCPConfig: mcpConfig,
        Logger:    bifrost.NewDefaultLogger(schemas.LogLevelInfo),
    })
    if err != nil {
        panic(err)
    }
}

Tools To Execute Semantics

The ToolsToExecute field controls which tools from the client are available:

Value	Behavior
`["*"]`	All tools from this client are included
`[]` or `nil`	No tools included (deny-by-default)
`["tool1", "tool2"]`	Only specified tools are included

Tools To Auto Execute (Agent Mode)

The ToolsToAutoExecute field controls which tools can be automatically executed in Agent Mode:

Value	Behavior
`["*"]`	All tools are auto-executed
`[]` or `nil`	No tools are auto-executed (manual approval required)
`["tool1", "tool2"]`	Only specified tools are auto-executed

A tool must be in both ToolsToExecute and ToolsToAutoExecute to be auto-executed. If a tool is in ToolsToAutoExecute but not in ToolsToExecute, it will be skipped.

Example configuration:

{
    Name:           "filesystem",
    ConnectionType: schemas.MCPConnectionTypeSTDIO,
    StdioConfig: &schemas.MCPStdioConfig{
        Command: "npx",
        Args:    []string{"-y", "@anthropic/mcp-filesystem"},
    },
    ToolsToExecute:     []string{"*"},                              // All tools available
    ToolsToAutoExecute: []string{"read_file", "list_directory"},    // Only these auto-execute
}

Environment Variables

Use environment variables for sensitive configuration values: Gateway (config.json):

{
  "name": "secure_api",
  "connection_type": "http",
  "connection_string": "env.SECURE_MCP_URL"
}

Go SDK:

{
    Name:             "secure_api",
    ConnectionType:   schemas.MCPConnectionTypeHTTP,
    ConnectionString: bifrost.Ptr(os.Getenv("SECURE_MCP_URL")),
}

Environment variables are:

Automatically resolved during client connection
Redacted in API responses and UI for security
Validated at startup to ensure all required variables are set

Client State Management

Connection States

State	Description
`connected`	Client is active and tools are available
`connecting`	Client is establishing connection
`disconnected`	Client lost connection but can be reconnected
`error`	Client configuration or connection failed

Managing Clients at Runtime

Gateway API
Go SDK

Reconnect a client:

curl -X POST http://localhost:8080/api/mcp/client/{id}/reconnect

Edit client configuration:

curl -X PUT http://localhost:8080/api/mcp/client/{id} \
  -H "Content-Type: application/json" \
  -d '{
    "name": "filesystem",
    "connection_type": "stdio",
    "stdio_config": {
      "command": "npx",
      "args": ["-y", "@anthropic/mcp-filesystem"]
    },
    "tools_to_execute": ["read_file", "list_directory"]
  }'

Remove a client:

curl -X DELETE http://localhost:8080/api/mcp/client/{id}

// Get all connected clients
clients, err := client.GetMCPClients()
for _, mcpClient := range clients {
    fmt.Printf("Client: %s, State: %s, Tools: %d\n",
        mcpClient.Config.Name,
        mcpClient.State,
        len(mcpClient.Tools))
}

// Reconnect a disconnected client
err = client.ReconnectMCPClient("filesystem")

// Add new client at runtime
err = client.AddMCPClient(schemas.MCPClientConfig{
    Name:           "new_client",
    ConnectionType: schemas.MCPConnectionTypeHTTP,
    ConnectionString: bifrost.Ptr("http://localhost:3002/mcp"),
    ToolsToExecute: []string{"*"},
})

// Remove a client
err = client.RemoveMCPClient("old_client")

// Edit client tools
err = client.EditMCPClientTools("filesystem", []string{"read_file", "list_directory"})

Health Monitoring

Bifrost automatically monitors MCP client health with periodic checks every 10 seconds by default.

Health Check Methods

By default, Bifrost uses the lightweight ping method for health checks. However, you can configure the health check method based on your MCP server’s capabilities:

Method	When to Use	Overhead	Fallback
Ping (default)	Server supports MCP ping protocol	Minimal	Best for most servers
ListTools	Server doesn’t support ping, or you need heavier checks	Higher	More resource-intensive

Configuring Health Check Method

You can toggle the is_ping_available setting for each client:

Via Web UI

Navigate to MCP Gateway and select a server
In the configuration panel, toggle “Ping Available for Health Check”
Enable: Uses lightweight ping for health checks
Disable: Uses listTools method for health checks instead

Via API

curl -X PUT http://localhost:8080/api/mcp/client/{id} \
  -H "Content-Type: application/json" \
  -d '{
    "name": "my_server",
    "is_ping_available": false
  }'

Via config.json

{
  "mcp": {
    "client_configs": [
      {
        "name": "filesystem",
        "connection_type": "stdio",
        "is_ping_available": true,
        "stdio_config": {
          "command": "npx",
          "args": ["-y", "@anthropic/mcp-filesystem"]
        }
      }
    ]
  }
}

Via Go SDK

err := client.EditMCPClient(context.Background(), schemas.MCPClientConfig{
    ID:               "filesystem",
    Name:             "filesystem",
    IsPingAvailable:  false,  // Use listTools instead of ping
    ToolsToExecute:   []string{"*"},
})

Health Check Behavior

When a client disconnects:

State changes to disconnected
Tools from that client become unavailable
You can reconnect via API or UI

Note: Changing is_ping_available takes effect immediately without requiring a client reconnection.

Connection Resilience and Retry Logic

Bifrost automatically implements exponential backoff retry logic to handle transient network failures and temporary service unavailability. This ensures that brief connection issues don’t immediately cause tool unavailability.

Important: Bifrost only retries on transient errors (network failures, timeouts, temporary service unavailability). Permanent errors like authentication failures, configuration errors, and missing commands fail immediately without retry.

Automatic Retry Strategy

Bifrost retries failed operations using the following strategy, as implemented by ExecuteWithRetry and DefaultRetryConfig in the MCP layer:

Parameter	Value	Description
Max Retries (`DefaultRetryConfig.MaxRetries`)	5	Retries after the initial attempt (6 attempts total)
Initial Backoff (`DefaultRetryConfig.InitialBackoff`)	1 second	Starting backoff duration before doubling
Max Backoff (`DefaultRetryConfig.MaxBackoff`)	30 seconds	Maximum wait time between retries
Backoff Multiplier	2x	Exponential growth between attempts

Backoff Progression (matches ExecuteWithRetry with DefaultRetryConfig):

Attempt 1: Initial attempt (no wait)
Attempt 2: Wait 1s, then retry (and double backoff to 2s)
Attempt 3: Wait 2s, then retry (and double backoff to 4s)
Attempt 4: Wait 4s, then retry (and double backoff to 8s)
Attempt 5: Wait 8s, then retry (and double backoff to 16s)
Attempt 6: Wait 16s, then retry (backoff capped at 30s max)

Error Classification

Bifrost intelligently classifies errors as either transient (retryable) or permanent (fail immediately): Transient Errors (Retried):

Connection timeouts or refused connections
Network unreachable errors
DNS resolution failures
HTTP 5xx errors (500, 502, 503, 504)
HTTP 429 (Too Many Requests)
I/O errors and broken pipes
Temporary service unavailability

Permanent Errors (Fail Immediately - No Retry):

Context deadline exceeded or cancelled - Retrying won’t help if time limit is reached
Authentication failures (401, 403)
Authorization denied
Configuration errors (invalid auth, invalid config)
File or command not found (e.g., “command not found: npx”)
Bad request errors (400, 405, 422)
Command execution permission denied
Invalid credentials

What Operations Are Retried

Bifrost applies retry logic to these critical operations:

Connection Creation - Establishing initial connection to the MCP server (with error classification)
Transport Start - Starting the transport layer (STDIO, HTTP, SSE)
Client Initialization - Initializing the MCP client protocol
Tool Discovery - Retrieving available tools from the server
Automatic Reconnection - When health checks detect disconnection

Reconnection on Health Check Failure

When a client reaches 5 consecutive health check failures:

Client state changes to disconnected
Bifrost automatically attempts reconnection in the background
Reconnection uses the same exponential backoff retry logic
Once reconnected, health checks resume normal operation
Tools become available again without manual intervention

This automatic reconnection happens asynchronously and doesn’t block other operations.

Manual Reconnection

You can also trigger manual reconnection at any time:

Gateway API
Go SDK

curl -X POST http://localhost:8080/api/mcp/client/{id}/reconnect

Manual reconnection also uses the retry logic for robustness.

// Reconnect with automatic retry logic
err := client.ReconnectMCPClient("filesystem")
if err != nil {
    log.Printf("Reconnection failed after retries: %v", err)
}

Benefits

Handles transient failures: Brief network hiccups won’t cause tool unavailability
Prevents server overload: Exponential backoff prevents hammering servers
Automatic recovery: Disconnected clients reconnect automatically
Production-ready: No manual intervention needed for temporary issues
Transparent logging: Detailed retry attempts logged for debugging

Naming Conventions

MCP client names have specific requirements:

Must contain only ASCII characters
Cannot contain hyphens (-) or spaces
Cannot start with a number
Must be unique across all clients

Valid names: filesystem, web_search, myAPI, tool123 Invalid names: my-tools, web search, 123tools, datos-api

Overview

Quick Start

Migration Guides

SDK Integrations

Providers & Guides

MCP Gateway

Custom plugins

Open Source Features

Enterprise Features

​Overview

​Connection Types

​STDIO Connections

​HTTP Connections

​Header-Based Authentication

​OAuth 2.0 Authentication

​SSE Connections

​Header-Based Authentication

​OAuth 2.0 Authentication

​Gateway Setup

​Adding an MCP Client

​Viewing and Managing Connected Tools

​Add STDIO Client

​Add HTTP Client

​Add SSE Client

​List All Clients

​Go SDK Setup

​Tools To Execute Semantics

​Tools To Auto Execute (Agent Mode)

​Environment Variables

​Client State Management

​Connection States

​Managing Clients at Runtime

​Health Monitoring

​Health Check Methods

​Configuring Health Check Method

​Via Web UI

​Via API

​Via config.json

​Via Go SDK

​Health Check Behavior

​Connection Resilience and Retry Logic

​Automatic Retry Strategy

​Error Classification

​What Operations Are Retried

​Reconnection on Health Check Failure

​Manual Reconnection

​Benefits

​Naming Conventions

​Next Steps

Tool Execution

Agent Mode

Overview

Connection Types

STDIO Connections

HTTP Connections

Header-Based Authentication

OAuth 2.0 Authentication

SSE Connections

Header-Based Authentication

OAuth 2.0 Authentication

Gateway Setup

Adding an MCP Client

Viewing and Managing Connected Tools

Add STDIO Client

Add HTTP Client

Add SSE Client

List All Clients

Go SDK Setup

Tools To Execute Semantics

Tools To Auto Execute (Agent Mode)

Environment Variables

Client State Management

Connection States

Managing Clients at Runtime

Health Monitoring

Health Check Methods

Configuring Health Check Method

Via Web UI

Via API

Via config.json

Via Go SDK

Health Check Behavior

Connection Resilience and Retry Logic

Automatic Retry Strategy

Error Classification

What Operations Are Retried

Reconnection on Health Check Failure

Manual Reconnection

Benefits

Naming Conventions

Next Steps