Clean up namespaces (#410)

No meaningful code changes, just lots of namespace shuffling to have fewer namespaces and to put things in better namespaces.

src/ModelContextProtocol/Protocol/Tool.cs

@@ -0,0 +1,78 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace ModelContextProtocol.Protocol;
+
+/// <summary>
+/// Represents a tool that the server is capable of calling.
+/// </summary>
+public class Tool
+{
+    private JsonElement _inputSchema = McpJsonUtilities.DefaultMcpToolSchema;
+
+    /// <summary>
+    /// Gets or sets the name of the tool.
+    /// </summary>
+    [JsonPropertyName("name")]
+    public string Name { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Gets or sets a human-readable description of the tool.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// This description helps the AI model understand what the tool does and when to use it.
+    /// It should be clear, concise, and accurately describe the tool's purpose and functionality.
+    /// </para>
+    /// <para>
+    /// The description is typically presented to AI models to help them determine when
+    /// and how to use the tool based on user requests.
+    /// </para>
+    /// </remarks>
+    [JsonPropertyName("description")]
+    public string? Description { get; set; }
+
+    /// <summary>
+    /// Gets or sets a JSON Schema object defining the expected parameters for the tool.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// The schema must be a valid JSON Schema object with the "type" property set to "object".
+    /// This is enforced by validation in the setter which will throw an <see cref="ArgumentException"/>
+    /// if an invalid schema is provided.
+    /// </para>
+    /// <para>
+    /// The schema typically defines the properties (parameters) that the tool accepts, 
+    /// their types, and which ones are required. This helps AI models understand
+    /// how to structure their calls to the tool.
+    /// </para>
+    /// <para>
+    /// If not explicitly set, a default minimal schema of <c>{"type":"object"}</c> is used.
+    /// </para>
+    /// </remarks>
+    [JsonPropertyName("inputSchema")]
+    public JsonElement InputSchema  
+    { 
+        get => _inputSchema; 
+        set
+        {
+            if (!McpJsonUtilities.IsValidMcpToolSchema(value))
+            {
+                throw new ArgumentException("The specified document is not a valid MCP tool JSON schema.", nameof(InputSchema));
+            }
+
+            _inputSchema = value;
+        }
+    }
+
+    /// <summary>
+    /// Gets or sets optional additional tool information and behavior hints.
+    /// </summary>
+    /// <remarks>
+    /// These annotations provide metadata about the tool's behavior, such as whether it's read-only,
+    /// destructive, idempotent, or operates in an open world. They also can include a human-readable title.
+    /// Note that these are hints and should not be relied upon for security decisions.
+    /// </remarks>
+    [JsonPropertyName("annotations")]
+    public ToolAnnotations? Annotations { get; set; }
+}