svrnty-mcp-server/samples/CodexMcpServer/Tools/GetDocumentTool.cs

using System;
using System.Net.Http;
using System.Text.Json;
using System.Threading.Tasks;
using Svrnty.MCP.Core;

namespace CodexMcpServer.Tools;

/// <summary>
/// MCP tool for retrieving a specific CODEX document by ID.
/// Calls CODEX API GET /api/documents/{id} endpoint.
/// </summary>
public class GetDocumentTool : IMcpTool
{
    private readonly HttpClient _httpClient;
    private static readonly JsonDocument _schema = JsonDocument.Parse("""
    {
        "type": "object",
        "properties": {
            "id": {
                "type": "string",
                "description": "Document ID to retrieve"
            }
        },
        "required": ["id"]
    }
    """);

    public GetDocumentTool(HttpClient httpClient)
    {
        _httpClient = httpClient ?? throw new ArgumentNullException(nameof(httpClient));

        // Set base address if not already set
        if (_httpClient.BaseAddress == null)
        {
            _httpClient.BaseAddress = new Uri("http://localhost:5050");
        }
    }

    /// <inheritdoc/>
    public string Name => "get_document";

    /// <inheritdoc/>
    public string Description => "Retrieve a specific CODEX document by ID. Returns complete document details including metadata, content, and sections.";

    /// <inheritdoc/>
    public JsonDocument Schema => _schema;

    /// <inheritdoc/>
    public async Task<JsonDocument> ExecuteAsync(JsonDocument? arguments)
    {
        try
        {
            // Validate arguments
            if (arguments == null)
            {
                return CreateErrorResponse("Arguments cannot be null. Expected {\"id\": \"document_id\"}");
            }

            var root = arguments.RootElement;
            if (!root.TryGetProperty("id", out var idElement))
            {
                return CreateErrorResponse("Missing required parameter 'id'");
            }

            var id = idElement.GetString();
            if (string.IsNullOrWhiteSpace(id))
            {
                return CreateErrorResponse("Document ID cannot be empty");
            }

            // Call CODEX API
            var response = await _httpClient.GetAsync($"/api/documents/{id}");

            if (!response.IsSuccessStatusCode)
            {
                var errorContent = await response.Content.ReadAsStringAsync();
                return CreateErrorResponse(
                    $"CODEX API returned error: {response.StatusCode}. {errorContent}"
                );
            }

            // Parse and return response
            var responseContent = await response.Content.ReadAsStringAsync();
            try
            {
                return JsonDocument.Parse(responseContent);
            }
            catch (JsonException ex)
            {
                return CreateErrorResponse($"Failed to parse CODEX API response: {ex.Message}");
            }
        }
        catch (HttpRequestException ex)
        {
            return CreateErrorResponse($"HTTP request failed: {ex.Message}");
        }
        catch (Exception ex)
        {
            return CreateErrorResponse($"Unexpected error: {ex.Message}");
        }
    }

    private static JsonDocument CreateErrorResponse(string message)
    {
        var error = new
        {
            error = message
        };
        return JsonDocument.Parse(JsonSerializer.Serialize(error));
    }
}