feat: Add tool annotations for improved LLM tool understanding

Add readOnlyHint and destructiveHint annotations to all tools
to help LLMs better understand tool behavior and make safer decisions.

Changes:
- Added readOnlyHint: true to read-only tools (conversations_history,
  conversations_replies, conversations_search_messages, channels_list)
- Added destructiveHint: true to conversations_add_message tool
- Added title annotations for human-readable display

This improves tool safety metadata for MCP clients by providing
semantic hints about whether tools modify data or just read it.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: web-flow

pkg/server/server.go

@@ -35,6 +35,8 @@ func NewMCPServer(provider *provider.ApiProvider, logger *zap.Logger) *MCPServer
 
 	s.AddTool(mcp.NewTool("conversations_history",
 		mcp.WithDescription("Get messages from the channel (or DM) by channel_id, the last row/column in the response is used as 'cursor' parameter for pagination if not empty"),
+		mcp.WithTitleAnnotation("Get Conversation History"),
+		mcp.WithReadOnlyHintAnnotation(true),
 		mcp.WithString("channel_id",
 			mcp.Required(),
 			mcp.Description("    - `channel_id` (string): ID of the channel in format Cxxxxxxxxxx or its name starting with #... or @... aka #general or @username_dm."),
@@ -54,6 +56,8 @@ func NewMCPServer(provider *provider.ApiProvider, logger *zap.Logger) *MCPServer
 
 	s.AddTool(mcp.NewTool("conversations_replies",
 		mcp.WithDescription("Get a thread of messages posted to a conversation by channelID and thread_ts, the last row/column in the response is used as 'cursor' parameter for pagination if not empty"),
+		mcp.WithTitleAnnotation("Get Thread Replies"),
+		mcp.WithReadOnlyHintAnnotation(true),
 		mcp.WithString("channel_id",
 			mcp.Required(),
 			mcp.Description("ID of the channel in format Cxxxxxxxxxx or its name starting with #... or @... aka #general or @username_dm."),
@@ -77,6 +81,8 @@ func NewMCPServer(provider *provider.ApiProvider, logger *zap.Logger) *MCPServer
 
 	s.AddTool(mcp.NewTool("conversations_add_message",
 		mcp.WithDescription("Add a message to a public channel, private channel, or direct message (DM, or IM) conversation by channel_id and thread_ts."),
+		mcp.WithTitleAnnotation("Send Message"),
+		mcp.WithDestructiveHintAnnotation(true),
 		mcp.WithString("channel_id",
 			mcp.Required(),
 			mcp.Description("ID of the channel in format Cxxxxxxxxxx or its name starting with #... or @... aka #general or @username_dm."),
@@ -95,6 +101,8 @@ func NewMCPServer(provider *provider.ApiProvider, logger *zap.Logger) *MCPServer
 
 	conversationsSearchTool := mcp.NewTool("conversations_search_messages",
 		mcp.WithDescription("Search messages in a public channel, private channel, or direct message (DM, or IM) conversation using filters. All filters are optional, if not provided then search_query is required."),
+		mcp.WithTitleAnnotation("Search Messages"),
+		mcp.WithReadOnlyHintAnnotation(true),
 		mcp.WithString("search_query",
 			mcp.Description("Search query to filter messages. Example: 'marketing report' or full URL of Slack message e.g. 'https://slack.com/archives/C1234567890/p1234567890123456', then the tool will return a single message matching given URL, herewith all other parameters will be ignored."),
 		),
@@ -143,6 +151,8 @@ func NewMCPServer(provider *provider.ApiProvider, logger *zap.Logger) *MCPServer
 
 	s.AddTool(mcp.NewTool("channels_list",
 		mcp.WithDescription("Get list of channels"),
+		mcp.WithTitleAnnotation("List Channels"),
+		mcp.WithReadOnlyHintAnnotation(true),
 		mcp.WithString("channel_types",
 			mcp.Required(),
 			mcp.Description("Comma-separated channel types. Allowed values: 'mpim', 'im', 'public_channel', 'private_channel'. Example: 'public_channel,private_channel,im'"),