feat(tools): add tool to get label_names

Signed-off-by: TJ Hoplock <[email protected]>

Author: tjhop

pkg/mcp/promapi.go

@@ -168,6 +168,25 @@ func seriesApiCall(ctx context.Context, matchers []string, start, end time.Time)
 	return string(jsonBytes), nil
 }
 
+func labelNamesApiCall(ctx context.Context, matchers []string, start, end time.Time) (string, error) {
+	result, warnings, err := apiV1Client.LabelNames(ctx, matchers, start, end)
+	if err != nil {
+		return "", fmt.Errorf("error getting label names: %w", err)
+	}
+
+	res := queryApiResponse{
+		Result:   strings.Join(result, "\n"),
+		Warnings: warnings,
+	}
+
+	jsonBytes, err := json.Marshal(res)
+	if err != nil {
+		return "", fmt.Errorf("error converting label names response to JSON: %w", err)
+	}
+
+	return string(jsonBytes), nil
+}
+
 func buildinfoApiCall(ctx context.Context) (string, error) {
 	ctx, cancel := context.WithTimeout(ctx, apiTimeout)
 	defer cancel()

pkg/mcp/server.go

@@ -28,6 +28,7 @@ func NewServer(logger *slog.Logger) *server.MCPServer {
 	mcpServer.AddTool(queryTool, queryToolHandler)
 	mcpServer.AddTool(rangeQueryTool, rangeQueryToolHandler)
 	mcpServer.AddTool(seriesTool, seriesToolHandler)
+	mcpServer.AddTool(labelNamesTool, labelNamesToolHandler)
 	mcpServer.AddTool(tsdbStatsTool, tsdbStatsToolHandler)
 	mcpServer.AddTool(listAlertsTool, listAlertsToolHandler)
 	mcpServer.AddTool(alertmanagersTool, alertmanagersToolHandler)

pkg/mcp/tools.go

@@ -61,6 +61,22 @@ var (
 			mcp.Description("[Optional] End timestamp for the query to be executed at."+
 				" Must be either Unix timestamp or RFC3339. Defaults to current time."),
 		),
+	)
+
+	labelNamesTool = mcp.NewTool("label_names",
+		mcp.WithDescription("Returns the unique label names present in the block in sorted order by given time range and matchers"),
+		mcp.WithArray("matchers",
+			mcp.Required(),
+			mcp.Description("Label matchers"),
+		),
+		mcp.WithString("start_time",
+			mcp.Description("[Optional] Start timestamp for the query to be executed at."+
+				" Must be either Unix timestamp or RFC3339. Defaults to 5m ago."),
+		),
+		mcp.WithString("end_time",
+			mcp.Required(),
+			mcp.Description("[Optional] End timestamp for the query to be executed at."+
+				" Must be either Unix timestamp or RFC3339. Defaults to current time."),
 		),
 	)
 
@@ -208,6 +224,43 @@ func seriesToolHandler(ctx context.Context, request mcp.CallToolRequest) (*mcp.C
 	return mcp.NewToolResultText(data), err
 }
 
+func labelNamesToolHandler(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+	arguments := request.Params.Arguments
+	argMatchers, ok := arguments["matchers"].([]any)
+	if !ok {
+		return nil, errors.New("matchers must be an array")
+	}
+
+	matchers := make([]string, len(argMatchers))
+	for i, m := range argMatchers {
+		matchers[i] = m.(string)
+	}
+
+	endTs := time.Now()
+	startTs := endTs.Add(DefaultLookbackDelta)
+
+	if argEndTime, ok := arguments["end_time"].(string); ok {
+		parsedEndTime, err := mcpProm.ParseTimestamp(argEndTime)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse end_time %s from args: %w", argEndTime, err)
+		}
+
+		endTs = parsedEndTime
+	}
+
+	if argStartTime, ok := arguments["start_time"].(string); ok {
+		parsedStartTime, err := mcpProm.ParseTimestamp(argStartTime)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse start_time %s from args: %w", argStartTime, err)
+		}
+
+		startTs = parsedStartTime
+	}
+
+	data, err := labelNamesApiCall(ctx, matchers, startTs, endTs)
+	return mcp.NewToolResultText(data), err
+}
+
 func listAlertsToolHandler(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
 	data, err := listAlertsApiCall(ctx)
 	return mcp.NewToolResultText(data), err