MCP Client — Connect to External MCP Servers

Granit.Mcp.Client provides a named factory for connecting to external MCP servers — ERP systems, data APIs, CLI tools, or any MCP-compatible service.

Installation

dotnet add package Granit.Mcp.Client

builder.AddGranitMcpClient();

Configuration

Named connections are configured in appsettings.json:

{
  "Mcp": {
    "Client": {
      "Connections": {
        "erp": {
          "Url": "https://erp.internal/mcp",
          "Transport": "http"
        },
        "data-tools": {
          "Transport": "stdio",
          "Command": "dotnet",
          "Arguments": ["run", "--project", "../DataTools/DataTools.csproj"]
        },
        "python-analyzer": {
          "Transport": "stdio",
          "Command": "python",
          "Arguments": ["-m", "analyzer_mcp"]
        }
      }
    }
  }
}

Connection options

Property	Type	Default	Required	Description
Url	string?	—	HTTP	Server URL (must use HTTPS in production)
Transport	string	"http"	—	"http" or "stdio"
AllowInsecureTransport	bool	false	—	Allow http:// (non-TLS) transport. Enable only for local development
Command	string?	—	stdio	Executable command
Arguments	string[]	[]	—	Command-line arguments

Usage

Basic client creation

public sealed class ExportService(IMcpClientFactory mcpFactory)
{
    public async Task<IReadOnlyList<McpClientTool>> GetErpToolsAsync(CancellationToken ct)
    {
        await using McpClient client = await mcpFactory.CreateAsync("erp", ct);
        return await client.ListToolsAsync(cancellationToken: ct);
    }

    public async Task<CallToolResult> InvokeErpToolAsync(
        string toolName, Dictionary<string, object?> args, CancellationToken ct)
    {
        await using McpClient client = await mcpFactory.CreateAsync("erp", ct);
        return await client.CallToolAsync(toolName, args, cancellationToken: ct);
    }
}

HTTP transport

For remote MCP servers accessible via HTTPS. The SDK uses Streamable HTTP (with automatic fallback to SSE for older servers):

{
  "erp": {
    "Url": "https://erp.internal/mcp"
  }
}

TLS required

HTTP connections require HTTPS by default. The factory throws InvalidOperationException if the URL uses http://. For local development (e.g., Ollama on http://localhost:11434), set "AllowInsecureTransport": true. Never enable this in production.

Stdio transport

For local tools running as child processes. The factory spawns the process and communicates via stdin/stdout:

{
  "local-tools": {
    "Transport": "stdio",
    "Command": "dotnet",
    "Arguments": ["run", "--project", "../InvoiceTools/"]
  }
}

Note

Stdio connections are local only — the child process runs on the same machine. Use HTTP transport for remote servers.

Error handling

The factory throws InvalidOperationException for configuration errors:

Scenario	Exception message
Connection not found	"MCP connection 'xyz' is not configured"
Unsupported transport	"Unsupported MCP transport type 'websocket'"
Missing URL (HTTP)	ArgumentException from ThrowIfNullOrWhiteSpace
Missing command (stdio)	ArgumentException from ThrowIfNullOrWhiteSpace

See also

• AI workspace integration — inject MCP tools into IChatClient
• Setup guide — server-side MCP configuration
• MCP overview — architecture and design principles