# OpenHarbor.MCP.Client - API Reference

**Version:** 1.0.0
**Last Updated:** 2025-10-19
**Status:** Production-Ready

---

## Table of Contents

- [Core Abstractions](#core-abstractions)
  - [IMcpClient](#imcpclient)
  - [IMcpServerConnection](#imcpserverconnection)
- [Infrastructure](#infrastructure)
  - [McpClient](#mcpclient)
  - [HttpServerConnection](#httpserverconnection)
- [Models](#models)
  - [ServerConnectionConfig](#serverconnectionconfig)
  - [McpToolInfo](#mcptoolinfo)
  - [McpToolResult](#mcptoolresult)
- [ASP.NET Core Integration](#aspnet-core-integration)
  - [Service Extensions](#service-extensions)
- [Configuration](#configuration)

---

## Core Abstractions

### IMcpClient

**Namespace:** `OpenHarbor.MCP.Client.Core.Abstractions`

Interface defining the MCP client contract for consuming MCP servers.

#### Methods

##### ConnectToServerAsync

```csharp
Task ConnectToServerAsync(
    string serverName,
    ServerConnectionConfig config,
    CancellationToken cancellationToken = default)
```

Establishes a connection to an MCP server.

**Parameters:**
- `serverName` (string): Unique identifier for this server
- `config` (ServerConnectionConfig): Connection configuration
- `cancellationToken` (CancellationToken): Optional cancellation token

**Throws:**
- `ConnectionException` - If connection fails
- `ArgumentException` - If server name already exists

**Example:**
```csharp
await client.ConnectToServerAsync(
    "codex-server",
    new ServerConnectionConfig
    {
        Transport = TransportType.Http,
        BaseUrl = "http://localhost:5050",
        Timeout = TimeSpan.FromSeconds(30)
    }
);
```

##### ListToolsAsync

```csharp
Task<IEnumerable<McpToolInfo>> ListToolsAsync(
    string serverName,
    CancellationToken cancellationToken = default)
```

Lists all tools available on a connected server.

**Parameters:**
- `serverName` (string): Name of the server to query
- `cancellationToken` (CancellationToken): Optional cancellation token

**Returns:** `Task<IEnumerable<McpToolInfo>>` - Collection of available tools

**Throws:**
- `ServerNotFoundException` - If server not connected
- `ConnectionException` - If connection lost

**Example:**
```csharp
var tools = await client.ListToolsAsync("codex-server");
foreach (var tool in tools)
{
    Console.WriteLine($"{tool.Name}: {tool.Description}");
}
```

##### CallToolAsync

```csharp
Task<McpToolResult> CallToolAsync(
    string serverName,
    string toolName,
    Dictionary<string, object> arguments,
    CancellationToken cancellationToken = default)
```

Calls a tool on a connected server.

**Parameters:**
- `serverName` (string): Name of the server hosting the tool
- `toolName` (string): Name of the tool to execute
- `arguments` (Dictionary<string, object>): Tool input parameters
- `cancellationToken` (CancellationToken): Optional cancellation token

**Returns:** `Task<McpToolResult>` - The result of the tool execution

**Throws:**
- `ServerNotFoundException` - If server not connected
- `ToolNotFoundException` - If tool doesn't exist
- `InvalidArgumentsException` - If arguments don't match schema
- `ConnectionException` - If connection lost

**Example:**
```csharp
var result = await client.CallToolAsync(
    serverName: "codex-server",
    toolName: "search_documents",
    arguments: new Dictionary<string, object>
    {
        ["query"] = "architecture patterns",
        ["maxResults"] = 10
    }
);

if (result.IsSuccess)
{
    Console.WriteLine(result.Content);
}
```

##### GetConnectedServersAsync

```csharp
Task<IEnumerable<ServerInfo>> GetConnectedServersAsync(
    CancellationToken cancellationToken = default)
```

Gets a list of all connected servers.

**Returns:** `Task<IEnumerable<ServerInfo>>` - Connected servers with status

**Example:**
```csharp
var servers = await client.GetConnectedServersAsync();
foreach (var server in servers)
{
    Console.WriteLine($"{server.Name}: {(server.IsHealthy ? "Healthy" : "Unhealthy")}");
}
```

##### DisconnectFromServerAsync

```csharp
Task DisconnectFromServerAsync(
    string serverName,
    CancellationToken cancellationToken = default)
```

Disconnects from a specific server.

**Parameters:**
- `serverName` (string): Name of the server to disconnect from
- `cancellationToken` (CancellationToken): Optional cancellation token

**Example:**
```csharp
await client.DisconnectFromServerAsync("codex-server");
```

---

### IMcpServerConnection

**Namespace:** `OpenHarbor.MCP.Client.Core.Abstractions`

Interface representing a connection to a single MCP server.

#### Properties

##### ServerName

```csharp
string ServerName { get; }
```

Unique identifier for this server connection.

##### IsConnected

```csharp
bool IsConnected { get; }
```

Indicates whether the connection is active.

##### Config

```csharp
ServerConnectionConfig Config { get; }
```

Configuration used for this connection.

#### Methods

##### SendRequestAsync

```csharp
Task<JsonRpcResponse> SendRequestAsync(
    JsonRpcRequest request,
    CancellationToken cancellationToken = default)
```

Sends a JSON-RPC request to the server.

**Parameters:**
- `request` (JsonRpcRequest): The request to send
- `cancellationToken` (CancellationToken): Cancellation support

**Returns:** `Task<JsonRpcResponse>` - The server response

**Example:**
```csharp
var request = new JsonRpcRequest
{
    JsonRpc = "2.0",
    Id = "1",
    Method = "tools/list"
};

var response = await connection.SendRequestAsync(request);
```

---

## Infrastructure

### McpClient

**Namespace:** `OpenHarbor.MCP.Client.Infrastructure`

Default implementation of `IMcpClient`.

#### Constructor

```csharp
public McpClient(ILogger<McpClient> logger = null)
```

**Parameters:**
- `logger` (ILogger<McpClient>): Optional logger instance

**Example:**
```csharp
var client = new McpClient();

// With logging
var loggerFactory = LoggerFactory.Create(builder =>
{
    builder.AddConsole();
});
var logger = loggerFactory.CreateLogger<McpClient>();
var clientWithLogging = new McpClient(logger);
```

#### Configuration

**Connection Pooling:**
```csharp
var client = new McpClient();
client.EnableConnectionPooling = true;
client.MaxConnectionsPerServer = 5;
client.ConnectionIdleTimeout = TimeSpan.FromMinutes(5);
```

**Retry Policy:**
```csharp
client.MaxRetries = 3;
client.RetryDelay = TimeSpan.FromSeconds(1);
client.RetryBackoff = RetryBackoffStrategy.Exponential;
```

---

### HttpServerConnection

**Namespace:** `OpenHarbor.MCP.Client.Infrastructure.Transports`

HTTP-based implementation of `IMcpServerConnection`.

#### Constructor

```csharp
public HttpServerConnection(
    string serverName,
    HttpServerConnectionConfig config,
    HttpClient httpClient = null)
```

**Parameters:**
- `serverName` (string): Server identifier
- `config` (HttpServerConnectionConfig): HTTP-specific configuration
- `httpClient` (HttpClient): Optional HttpClient (for DI)

**Example:**
```csharp
var config = new HttpServerConnectionConfig
{
    ServerUrl = "http://localhost:5050",
    Timeout = TimeSpan.FromSeconds(30),
    ApiKey = Environment.GetEnvironmentVariable("MCP_API_KEY")
};

var connection = new HttpServerConnection("codex-server", config);
await connection.ConnectAsync();
```

#### Configuration Options

```csharp
public class HttpServerConnectionConfig : ServerConnectionConfig
{
    public string ServerUrl { get; set; }
    public string ApiKey { get; set; }
    public Dictionary<string, string> Headers { get; set; }
    public TimeSpan Timeout { get; set; }
    public bool ValidateSslCertificate { get; set; }
}
```

---

## Models

### ServerConnectionConfig

**Namespace:** `OpenHarbor.MCP.Client.Core.Models`

Base configuration for server connections.

#### Properties

```csharp
public class ServerConnectionConfig
{
    public TransportType Transport { get; set; }
    public TimeSpan Timeout { get; set; }
    public bool Enabled { get; set; }
}

public enum TransportType
{
    Http,
    Stdio
}
```

#### Example

```csharp
var config = new ServerConnectionConfig
{
    Transport = TransportType.Http,
    Timeout = TimeSpan.FromSeconds(30),
    Enabled = true
};
```

---

### McpToolInfo

**Namespace:** `OpenHarbor.MCP.Client.Core.Models`

Metadata about an available tool.

#### Properties

```csharp
public class McpToolInfo
{
    public string Name { get; set; }
    public string Description { get; set; }
    public McpToolSchema InputSchema { get; set; }
}
```

#### Example

```csharp
var toolInfo = new McpToolInfo
{
    Name = "search_documents",
    Description = "Search documents by query",
    InputSchema = new McpToolSchema { ... }
};
```

---

### McpToolResult

**Namespace:** `OpenHarbor.MCP.Client.Core.Models`

Result of a tool execution.

#### Properties

```csharp
public class McpToolResult
{
    public bool IsSuccess { get; set; }
    public string Content { get; set; }
    public string ErrorMessage { get; set; }
    public int? ErrorCode { get; set; }
}
```

#### Usage

```csharp
var result = await client.CallToolAsync(...);

if (result.IsSuccess)
{
    Console.WriteLine($"Success: {result.Content}");
}
else
{
    Console.WriteLine($"Error {result.ErrorCode}: {result.ErrorMessage}");
}
```

---

## ASP.NET Core Integration

### Service Extensions

**Namespace:** `OpenHarbor.MCP.Client.AspNetCore`

#### AddMcpClient

```csharp
public static IServiceCollection AddMcpClient(
    this IServiceCollection services,
    IConfiguration configuration)
```

Registers MCP client and dependencies from configuration.

**Configuration Format:**
```json
{
  "Mcp": {
    "Client": {
      "Name": "MyAppClient",
      "Version": "1.0.0"
    },
    "Servers": [
      {
        "Name": "codex-server",
        "Transport": {
          "Type": "Http",
          "BaseUrl": "http://localhost:5050"
        },
        "Timeout": "00:00:30",
        "Enabled": true
      }
    ]
  }
}
```

**Example:**
```csharp
var builder = WebApplication.CreateBuilder(args);

builder.Services.AddMcpClient(
    builder.Configuration.GetSection("Mcp")
);

var app = builder.Build();
```

#### Dependency Injection

```csharp
public class MyService
{
    private readonly IMcpClient _mcpClient;

    public MyService(IMcpClient mcpClient)
    {
        _mcpClient = mcpClient;
    }

    public async Task<string> SearchAsync(string query)
    {
        var result = await _mcpClient.CallToolAsync(
            "codex-server",
            "search_documents",
            new Dictionary<string, object> { ["query"] = query }
        );

        return result.Content;
    }
}
```

---

## Configuration

### appsettings.json Structure

```json
{
  "Mcp": {
    "Client": {
      "Name": "MyApplication",
      "Version": "1.0.0",
      "Description": "My MCP client application"
    },
    "Servers": [
      {
        "Name": "codex-server",
        "Transport": {
          "Type": "Http",
          "BaseUrl": "http://localhost:5050"
        },
        "Timeout": "00:00:30",
        "Enabled": true
      }
    ],
    "Connection": {
      "MaxRetries": 3,
      "RetryDelayMs": 1000,
      "EnableConnectionPooling": true,
      "MaxConnectionsPerServer": 5,
      "ConnectionIdleTimeout": "00:05:00"
    }
  }
}
```

### Environment Variables

Override configuration with environment variables:

```bash
export MCP__SERVERS__0__TRANSPORT__BASEURL="https://production.example.com"
export MCP__CONNECTION__MAXRETRIES="5"
```

---

## Error Handling

### Exception Hierarchy

```
McpException (base)
├── ConnectionException
│   ├── ServerNotFoundException
│   ├── ConnectionTimeoutException
│   └── ServerUnavailableException
├── ToolException
│   ├── ToolNotFoundException
│   └── InvalidArgumentsException
└── TransportException
    ├── HttpTransportException
    └── StdioTransportException
```

### Example Error Handling

```csharp
try
{
    var result = await client.CallToolAsync(...);
}
catch (ServerNotFoundException ex)
{
    _logger.LogError($"Server not found: {ex.ServerName}");
}
catch (ToolNotFoundException ex)
{
    _logger.LogError($"Tool not found: {ex.ToolName}");
}
catch (ConnectionTimeoutException ex)
{
    _logger.LogWarning($"Timeout connecting to {ex.ServerName}");
    // Retry logic
}
catch (McpException ex)
{
    _logger.LogError($"MCP error: {ex.Message}");
}
```

---

## Complete Example

### Console Application

```csharp
using OpenHarbor.MCP.Client.Core;
using OpenHarbor.MCP.Client.Infrastructure;

class Program
{
    static async Task Main(string[] args)
    {
        // 1. Create client
        var client = new McpClient();

        // 2. Connect to server
        await client.ConnectToServerAsync(
            "codex-server",
            new ServerConnectionConfig
            {
                Transport = TransportType.Http,
                BaseUrl = "http://localhost:5050",
                Timeout = TimeSpan.FromSeconds(30)
            }
        );

        // 3. List available tools
        var tools = await client.ListToolsAsync("codex-server");
        Console.WriteLine($"Found {tools.Count()} tools:");
        foreach (var tool in tools)
        {
            Console.WriteLine($"  - {tool.Name}: {tool.Description}");
        }

        // 4. Call a tool
        var result = await client.CallToolAsync(
            serverName: "codex-server",
            toolName: "search_documents",
            arguments: new Dictionary<string, object>
            {
                ["query"] = "architecture",
                ["maxResults"] = 5
            }
        );

        // 5. Handle result
        if (result.IsSuccess)
        {
            Console.WriteLine($"Results: {result.Content}");
        }
        else
        {
            Console.WriteLine($"Error: {result.ErrorMessage}");
        }

        // 6. Disconnect
        await client.DisconnectFromServerAsync("codex-server");
    }
}
```

### ASP.NET Core Web API

```csharp
[ApiController]
[Route("api/[controller]")]
public class SearchController : ControllerBase
{
    private readonly IMcpClient _mcpClient;

    public SearchController(IMcpClient mcpClient)
    {
        _mcpClient = mcpClient;
    }

    [HttpGet]
    public async Task<IActionResult> Search([FromQuery] string query)
    {
        try
        {
            var result = await _mcpClient.CallToolAsync(
                "codex-server",
                "search_documents",
                new Dictionary<string, object> { ["query"] = query }
            );

            if (result.IsSuccess)
            {
                return Ok(result.Content);
            }

            return StatusCode(500, result.ErrorMessage);
        }
        catch (ServerNotFoundException ex)
        {
            return NotFound($"Server not found: {ex.ServerName}");
        }
        catch (Exception ex)
        {
            return StatusCode(500, ex.Message);
        }
    }
}
```

---

## See Also

- [Client Architecture](../architecture.md)
- [Module Design](../module-design.md)
- [Implementation Plan](../implementation-plan.md)
- [AGENT-PRIMER.md](../../AGENT-PRIMER.md)

---

**Document Type:** API Reference
**Version:** 1.0.0
**Last Updated:** 2025-10-19
**Maintained By:** Svrnty Development Team